diff --git a/CHANGELOG.md b/CHANGELOG.md
index db04f93..b11f044 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,9 @@
+# 3.0.0
+1. Separated Metadata from Objects (removed `metadata` from `Persistable`)
+2. Updated for Swift 3.0
+3. Pod name changed to RCSYapDatabaseExtensions
+4. Use `map` instead of `flatMap` when reading multiple objects so the order of the output corresponds to the order of the input.
+
 # 2.6.0
 Updated for Swift 2.3 - sorry it's taken so long!
 
diff --git a/Cartfile b/Cartfile
index 034481a..00e0c1c 100644
--- a/Cartfile
+++ b/Cartfile
@@ -1,3 +1,2 @@
-github "danthorpe/ValueCoding" "1.5.0"
-github "CocoaLumberjack/CocoaLumberjack" "2.4.0"
-github "yapstudios/YapDatabase" "2.9.2"
\ No newline at end of file
+github "danthorpe/ValueCoding" "2.1.0"
+github "yapstudios/YapDatabase" "2.9.3"
\ No newline at end of file
diff --git a/Cartfile.resolved b/Cartfile.resolved
index 8ae8b91..f10e04c 100644
--- a/Cartfile.resolved
+++ b/Cartfile.resolved
@@ -1,4 +1,3 @@
-github "CocoaLumberjack/CocoaLumberjack" "2.4.0"
-github "tonymillion/Reachability" "c4d225a479379f9998dbd5b55070427373d20574"
-github "danthorpe/ValueCoding" "1.5.0"
-github "yapstudios/YapDatabase" "2.9.2"
+github "CocoaLumberjack/CocoaLumberjack" "3.0.0"
+github "danthorpe/ValueCoding" "2.1.0"
+github "yapstudios/YapDatabase" "2.9.3"
diff --git a/Gemfile.lock b/Gemfile.lock
index b7cdf05..911cca6 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -55,9 +55,9 @@ GEM
       netrc (= 0.7.8)
     cocoapods-try (1.1.0)
     colored (1.2)
-    commander (4.4.1)
+    commander (4.4.3)
       highline (~> 1.7.2)
-    credentials_manager (0.16.2)
+    credentials_manager (0.16.4)
       colored
       commander (>= 4.3.5)
       highline (>= 1.7.1)
@@ -299,9 +299,10 @@ PLATFORMS
 DEPENDENCIES
   cocoapods
   cocoapods-keys
+  credentials_manager (= 0.16.4)
   fastlane
   slather
   xcpretty
 
 BUNDLED WITH
-   1.13.6
+   1.13.7
diff --git a/YapDatabaseExtensions.podspec b/RCSYapDatabaseExtensions.podspec
similarity index 50%
rename from YapDatabaseExtensions.podspec
rename to RCSYapDatabaseExtensions.podspec
index c2da953..013359a 100644
--- a/YapDatabaseExtensions.podspec
+++ b/RCSYapDatabaseExtensions.podspec
@@ -1,30 +1,30 @@
 Pod::Spec.new do |s|
-  s.name              = "YapDatabaseExtensions"
-  s.version           = "2.6.0"
+  s.name              = "RCSYapDatabaseExtensions"
+  s.version           = "3.0.0"
   s.summary           = "Helpers for using value types with YapDatabase."
   s.description       = <<-DESC
   
   Defines APIs to conveniently read, write and remove objects and values
   to or from YapDatabse. See ValueCoding for value type support.
+  
+  Fork of danthorpe's YapDatabaseExtensions with Swift 3 support and
+  metadata separated from objects.
 
                        DESC
-  s.homepage          = "https://github.com/danthorpe/YapDatabaseExtensions"
+  s.homepage          = "https://github.com/JimRoepcke/YapDatabaseExtensions"
   s.license           = 'MIT'
-  s.author            = { "Daniel Thorpe" => "@danthorpe" }
-  s.source            = { :git => "https://github.com/danthorpe/YapDatabaseExtensions.git", :tag => s.version.to_s }
-  s.module_name       = 'YapDatabaseExtensions'
-  s.social_media_url  = 'https://twitter.com/danthorpe'
+  s.authors           = { "Daniel Thorpe" => "@danthorpe", "Jim Roepcke" => "@JimRoepcke" }
+  s.source            = { :git => "https://github.com/JimRoepcke/YapDatabaseExtensions.git", :tag => s.version.to_s }
+  s.module_name       = 'RCSYapDatabaseExtensions'
+  s.social_media_url  = 'https://twitter.com/JimRoepcke'
   s.requires_arc      = true
   s.default_subspec   = 'Persitable'
-  s.ios.deployment_target = '8.0'
-  s.osx.deployment_target = '10.10'
+  s.ios.deployment_target = '9.0'
+  s.osx.deployment_target = '10.11'
 
-  s.dependency 'ValueCoding', '~> 1.5'
+  s.dependency 'ValueCoding', '~> 2.1.0'
   s.dependency 'YapDatabase', '2.9.2'
   
-  # Ensure the correct version of Swift is used
-  s.pod_target_xcconfig = { 'SWIFT_VERSION' => '2.3' }  
-  
   s.subspec 'Core' do |ss|
     ss.source_files = [
       'Sources/YapDatabaseExtensions.swift',
@@ -33,12 +33,12 @@ Pod::Spec.new do |s|
   end
   
   s.subspec 'Functional' do |ss|
-    ss.dependency 'YapDatabaseExtensions/Core'
+    ss.dependency 'RCSYapDatabaseExtensions/Core'
     ss.source_files = 'Sources/Functional_*.swift'
   end
 
   s.subspec 'Persitable' do |ss|
-    ss.dependency 'YapDatabaseExtensions/Functional'
+    ss.dependency 'RCSYapDatabaseExtensions/Functional'
     ss.source_files = [
       'Sources/Read.swift', 
       'Sources/Persistable_*.swift'
diff --git a/Sources/Curried_ObjectWithNoMetadata.swift b/Sources/Curried_ObjectWithNoMetadata.swift
index 4ec7b60..6429cb5 100644
--- a/Sources/Curried_ObjectWithNoMetadata.swift
+++ b/Sources/Curried_ObjectWithNoMetadata.swift
@@ -22,8 +22,8 @@ extension Persistable where
     - returns: a (ReadTransaction) -> Self? closure.
     */
     public static func readAtIndex<
-        ReadTransaction where
-        ReadTransaction: ReadTransactionType>(index: YapDB.Index) -> ReadTransaction -> Self? {
+        ReadTransaction>(_ index: YapDB.Index) -> (ReadTransaction) -> Self? where
+        ReadTransaction: ReadTransactionType {
             return { $0.readAtIndex(index) }
     }
 
@@ -35,10 +35,10 @@ extension Persistable where
     - returns: a (ReadTransaction) -> [Self] closure.
     */
     public static func readAtIndexes<
-        Indexes, ReadTransaction where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
-        ReadTransaction: ReadTransactionType>(indexes: Indexes) -> ReadTransaction -> [Self] {
+        Indexes, ReadTransaction>(_ indexes: Indexes) -> (ReadTransaction) -> [Self?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
+        ReadTransaction: ReadTransactionType {
             return { $0.readAtIndexes(indexes) }
     }
 
@@ -50,8 +50,8 @@ extension Persistable where
     - returns: a (ReadTransaction) -> Self? closure.
     */
     public static func readByKey<
-        ReadTransaction where
-        ReadTransaction: ReadTransactionType>(key: String) -> ReadTransaction -> Self? {
+        ReadTransaction>(_ key: String) -> (ReadTransaction) -> Self? where
+        ReadTransaction: ReadTransactionType {
             return { $0.readByKey(key) }
     }
 
@@ -63,10 +63,10 @@ extension Persistable where
     - returns: a (ReadTransaction) -> [Self] closure.
     */
     public static func readByKeys<
-        Keys, ReadTransaction where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
-        ReadTransaction: ReadTransactionType>(keys: Keys) -> ReadTransaction -> [Self] {
+        Keys, ReadTransaction>(_ keys: Keys) -> (ReadTransaction) -> [Self?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
+        ReadTransaction: ReadTransactionType {
             return  { $0.readAtIndexes(Self.indexesWithKeys(keys)) }
     }
 
@@ -77,7 +77,7 @@ extension Persistable where
     - warning: Be aware that this will capure `self`.
     - returns: a (WriteTransaction) -> Self closure
     */
-    public func write<WriteTransaction: WriteTransactionType>() -> WriteTransaction -> Self {
+    public func write<WriteTransaction: WriteTransactionType>() -> (WriteTransaction) -> Self {
         return { $0.write(self) }
     }
 }
diff --git a/Sources/Curried_ObjectWithObjectMetadata.swift b/Sources/Curried_ObjectWithObjectMetadata.swift
index 77587cb..9ea47fe 100644
--- a/Sources/Curried_ObjectWithObjectMetadata.swift
+++ b/Sources/Curried_ObjectWithObjectMetadata.swift
@@ -22,9 +22,9 @@ extension Persistable where
     - returns: a (ReadTransaction) -> Self? closure.
     */
     public static func readWithMetadataAtIndex<
-        ReadTransaction, Metadata where
+        ReadTransaction, Metadata>(_ index: YapDB.Index) -> (ReadTransaction) -> YapItem<Self, Metadata>? where
         ReadTransaction: ReadTransactionType,
-        Metadata: NSCoding>(index: YapDB.Index) -> ReadTransaction -> YapItem<Self, Metadata>? {
+        Metadata: NSCoding {
         return { $0.readWithMetadataAtIndex(index) }
     }
 
@@ -36,11 +36,11 @@ extension Persistable where
     - returns: a (ReadTransaction) -> [Self] closure.
     */
     public static func readWithMetadataAtIndexes<
-        Indexes, ReadTransaction, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, ReadTransaction, Metadata>(_ indexes: Indexes) -> (ReadTransaction) -> [YapItem<Self, Metadata>?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         ReadTransaction: ReadTransactionType,
-        Metadata: NSCoding>(indexes: Indexes) -> ReadTransaction -> [YapItem<Self, Metadata>] {
+        Metadata: NSCoding {
         return { $0.readWithMetadataAtIndexes(indexes) }
     }
 
@@ -52,9 +52,9 @@ extension Persistable where
     - returns: a (ReadTransaction) -> Self? closure.
     */
     public static func readWithMetadataByKey<
-        ReadTransaction, Metadata where
+        ReadTransaction, Metadata>(_ key: String) -> (ReadTransaction) -> YapItem<Self, Metadata>? where
         ReadTransaction: ReadTransactionType,
-        Metadata: NSCoding>(key: String) -> ReadTransaction -> YapItem<Self, Metadata>? {
+        Metadata: NSCoding {
         return { $0.readWithMetadataByKey(key) }
     }
 
@@ -66,11 +66,11 @@ extension Persistable where
     - returns: a (ReadTransaction) -> [Self] closure.
     */
     public static func readWithMetadataByKeys<
-        Keys, ReadTransaction, Metadata where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
+        Keys, ReadTransaction, Metadata>(_ keys: Keys) -> (ReadTransaction) -> [YapItem<Self, Metadata>?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
         ReadTransaction: ReadTransactionType,
-        Metadata: NSCoding>(keys: Keys) -> ReadTransaction -> [YapItem<Self, Metadata>] {
+        Metadata: NSCoding {
         return  { $0.readWithMetadataAtIndexes(Self.indexesWithKeys(keys)) }
     }
 
@@ -82,9 +82,9 @@ extension Persistable where
     - returns: a (WriteTransaction) -> Self closure
     */
     public func writeWithMetadata<
-        WriteTransaction, Metadata where
+        WriteTransaction, Metadata>(_ metadata: Metadata? = nil) -> (WriteTransaction) -> YapItem<Self, Metadata> where
         WriteTransaction: WriteTransactionType,
-        Metadata: NSCoding>(metadata: Metadata? = nil) -> WriteTransaction -> YapItem<Self, Metadata> {
+        Metadata: NSCoding {
         return { $0.writeWithMetadata(YapItem(self, metadata)) }
     }
 }
diff --git a/Sources/Curried_ObjectWithValueMetadata.swift b/Sources/Curried_ObjectWithValueMetadata.swift
index 9dd1702..be14cda 100644
--- a/Sources/Curried_ObjectWithValueMetadata.swift
+++ b/Sources/Curried_ObjectWithValueMetadata.swift
@@ -22,11 +22,11 @@ extension Persistable where
     - returns: a (ReadTransaction) -> Self? closure.
     */
     public static func readWithMetadataAtIndex<
-        ReadTransaction, Metadata where
+        ReadTransaction, Metadata>(_ index: YapDB.Index) -> (ReadTransaction) -> YapItem<Self, Metadata>? where
         ReadTransaction: ReadTransactionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(index: YapDB.Index) -> ReadTransaction -> YapItem<Self, Metadata>? {
+        Metadata.Coder.Value == Metadata {
             return { $0.readWithMetadataAtIndex(index) }
     }
 
@@ -38,13 +38,13 @@ extension Persistable where
     - returns: a (ReadTransaction) -> [Self] closure.
     */
     public static func readWithMetadataAtIndexes<
-        Indexes, ReadTransaction, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, ReadTransaction, Metadata>(_ indexes: Indexes) -> (ReadTransaction) -> [YapItem<Self, Metadata>?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         ReadTransaction: ReadTransactionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(indexes: Indexes) -> ReadTransaction -> [YapItem<Self, Metadata>] {
+        Metadata.Coder.Value == Metadata {
             return { $0.readWithMetadataAtIndexes(indexes) }
     }
 
@@ -56,11 +56,11 @@ extension Persistable where
     - returns: a (ReadTransaction) -> Self? closure.
     */
     public static func readWithMetadataByKey<
-        ReadTransaction, Metadata where
+        ReadTransaction, Metadata>(_ key: String) -> (ReadTransaction) -> YapItem<Self, Metadata>? where
         ReadTransaction: ReadTransactionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(key: String) -> ReadTransaction -> YapItem<Self, Metadata>? {
+        Metadata.Coder.Value == Metadata {
             return { $0.readWithMetadataByKey(key) }
     }
 
@@ -72,13 +72,13 @@ extension Persistable where
     - returns: a (ReadTransaction) -> [Self] closure.
     */
     public static func readWithMetadataByKeys<
-        Keys, ReadTransaction, Metadata where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
+        Keys, ReadTransaction, Metadata>(_ keys: Keys) -> (ReadTransaction) -> [YapItem<Self, Metadata>?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
         ReadTransaction: ReadTransactionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(keys: Keys) -> ReadTransaction -> [YapItem<Self, Metadata>] {
+        Metadata.Coder.Value == Metadata {
             return  { $0.readWithMetadataAtIndexes(Self.indexesWithKeys(keys)) }
     }
 
@@ -90,11 +90,11 @@ extension Persistable where
     - returns: a (WriteTransaction) -> Self closure
     */
     public func writeWithMetadata<
-        WriteTransaction, Metadata where
+        WriteTransaction, Metadata>(_ metadata: Metadata? = nil) -> (WriteTransaction) -> YapItem<Self, Metadata> where
         WriteTransaction: WriteTransactionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(metadata: Metadata? = nil) -> WriteTransaction -> YapItem<Self, Metadata> {
+        Metadata.Coder.Value == Metadata {
         return { $0.writeWithMetadata(YapItem(self, metadata)) }
     }
 }
diff --git a/Sources/Curried_ValueWithNoMetadata.swift b/Sources/Curried_ValueWithNoMetadata.swift
index 60cd00a..cf5eab8 100644
--- a/Sources/Curried_ValueWithNoMetadata.swift
+++ b/Sources/Curried_ValueWithNoMetadata.swift
@@ -14,7 +14,7 @@ import ValueCoding
 extension Persistable where
     Self: ValueCoding,
     Self.Coder: NSCoding,
-    Self.Coder.ValueType == Self {
+    Self.Coder.Value == Self {
 
     /**
     Returns a closure which, given a read transaction will return
@@ -24,8 +24,8 @@ extension Persistable where
     - returns: a (ReadTransaction) -> Self? closure.
     */
     public static func readAtIndex<
-        ReadTransaction where
-        ReadTransaction: ReadTransactionType>(index: YapDB.Index) -> ReadTransaction -> Self? {
+        ReadTransaction>(_ index: YapDB.Index) -> (ReadTransaction) -> Self? where
+        ReadTransaction: ReadTransactionType {
             return { $0.readAtIndex(index) }
     }
 
@@ -37,10 +37,10 @@ extension Persistable where
     - returns: a (ReadTransaction) -> [Self] closure.
     */
     public static func readAtIndexes<
-        Indexes, ReadTransaction where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
-        ReadTransaction: ReadTransactionType>(indexes: Indexes) -> ReadTransaction -> [Self] {
+        Indexes, ReadTransaction>(_ indexes: Indexes) -> (ReadTransaction) -> [Self?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
+        ReadTransaction: ReadTransactionType {
             return { $0.readAtIndexes(indexes) }
     }
 
@@ -52,8 +52,8 @@ extension Persistable where
     - returns: a (ReadTransaction) -> Self? closure.
     */
     public static func readByKey<
-        ReadTransaction where
-        ReadTransaction: ReadTransactionType>(key: String) -> ReadTransaction -> Self? {
+        ReadTransaction>(_ key: String) -> (ReadTransaction) -> Self? where
+        ReadTransaction: ReadTransactionType {
             return { $0.readByKey(key) }
     }
 
@@ -65,10 +65,10 @@ extension Persistable where
     - returns: a (ReadTransaction) -> [Self] closure.
     */
     public static func readByKeys<
-        Keys, ReadTransaction where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
-        ReadTransaction: ReadTransactionType>(keys: Keys) -> ReadTransaction -> [Self] {
+        Keys, ReadTransaction>(_ keys: Keys) -> (ReadTransaction) -> [Self?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
+        ReadTransaction: ReadTransactionType {
             return  { $0.readAtIndexes(Self.indexesWithKeys(keys)) }
     }
 
@@ -79,7 +79,7 @@ extension Persistable where
     - warning: Be aware that this will capure `self`.
     - returns: a (WriteTransaction) -> Self closure
     */
-    public func write<WriteTransaction: WriteTransactionType>() -> WriteTransaction -> Self {
+    public func write<WriteTransaction: WriteTransactionType>() -> (WriteTransaction) -> Self {
         return { $0.write(self) }
     }
 }
diff --git a/Sources/Curried_ValueWithObjectMetadata.swift b/Sources/Curried_ValueWithObjectMetadata.swift
index 6ff0779..26ce801 100644
--- a/Sources/Curried_ValueWithObjectMetadata.swift
+++ b/Sources/Curried_ValueWithObjectMetadata.swift
@@ -14,7 +14,7 @@ import ValueCoding
 extension Persistable where
     Self: ValueCoding,
     Self.Coder: NSCoding,
-    Self.Coder.ValueType == Self {
+    Self.Coder.Value == Self {
 
     /**
     Returns a closure which, given a read transaction will return
@@ -24,9 +24,9 @@ extension Persistable where
     - returns: a (ReadTransaction) -> Self? closure.
     */
     public static func readWithMetadataAtIndex<
-        ReadTransaction, Metadata where
+        ReadTransaction, Metadata>(_ index: YapDB.Index) -> (ReadTransaction) -> YapItem<Self, Metadata>? where
         ReadTransaction: ReadTransactionType,
-        Metadata: NSCoding>(index: YapDB.Index) -> ReadTransaction -> YapItem<Self, Metadata>? {
+        Metadata: NSCoding {
         return { $0.readWithMetadataAtIndex(index) }
     }
 
@@ -38,11 +38,11 @@ extension Persistable where
     - returns: a (ReadTransaction) -> [Self] closure.
     */
     public static func readWithMetadataAtIndexes<
-        Indexes, ReadTransaction, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, ReadTransaction, Metadata>(_ indexes: Indexes) -> (ReadTransaction) -> [YapItem<Self, Metadata>?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         ReadTransaction: ReadTransactionType,
-        Metadata: NSCoding>(indexes: Indexes) -> ReadTransaction -> [YapItem<Self, Metadata>] {
+        Metadata: NSCoding {
         return { $0.readWithMetadataAtIndexes(indexes) }
     }
 
@@ -54,9 +54,9 @@ extension Persistable where
     - returns: a (ReadTransaction) -> Self? closure.
     */
     public static func readWithMetadataByKey<
-        ReadTransaction, Metadata where
+        ReadTransaction, Metadata>(_ key: String) -> (ReadTransaction) -> YapItem<Self, Metadata>? where
         ReadTransaction: ReadTransactionType,
-        Metadata: NSCoding>(key: String) -> ReadTransaction -> YapItem<Self, Metadata>? {
+        Metadata: NSCoding {
         return { $0.readWithMetadataByKey(key) }
     }
 
@@ -68,11 +68,11 @@ extension Persistable where
     - returns: a (ReadTransaction) -> [Self] closure.
     */
     public static func readWithMetadataByKeys<
-        Keys, ReadTransaction, Metadata where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
+        Keys, ReadTransaction, Metadata>(_ keys: Keys) -> (ReadTransaction) -> [YapItem<Self, Metadata>?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
         ReadTransaction: ReadTransactionType,
-        Metadata: NSCoding>(keys: Keys) -> ReadTransaction -> [YapItem<Self, Metadata>] {
+        Metadata: NSCoding {
         return  { $0.readWithMetadataAtIndexes(Self.indexesWithKeys(keys)) }
     }
 
@@ -84,9 +84,9 @@ extension Persistable where
     - returns: a (WriteTransaction) -> Self closure
     */
     public func writeWithMetadata<
-        WriteTransaction, Metadata where
+        WriteTransaction, Metadata>(_ metadata: Metadata? = nil) -> (WriteTransaction) -> YapItem<Self, Metadata> where
         WriteTransaction: WriteTransactionType,
-        Metadata: NSCoding>(metadata: Metadata? = nil) -> WriteTransaction -> YapItem<Self, Metadata> {
+        Metadata: NSCoding {
         return { $0.writeWithMetadata(YapItem(self, metadata)) }
     }
 }
diff --git a/Sources/Curried_ValueWithValueMetadata.swift b/Sources/Curried_ValueWithValueMetadata.swift
index 4525175..8043070 100644
--- a/Sources/Curried_ValueWithValueMetadata.swift
+++ b/Sources/Curried_ValueWithValueMetadata.swift
@@ -14,7 +14,7 @@ import ValueCoding
 extension Persistable where
     Self: ValueCoding,
     Self.Coder: NSCoding,
-    Self.Coder.ValueType == Self {
+    Self.Coder.Value == Self {
 
     /**
     Returns a closure which, given a read transaction will return
@@ -24,11 +24,11 @@ extension Persistable where
     - returns: a (ReadTransaction) -> Self? closure.
     */
     public static func readWithMetadataAtIndex<
-        ReadTransaction, Metadata where
+        ReadTransaction, Metadata>(_ index: YapDB.Index) -> (ReadTransaction) -> YapItem<Self, Metadata>? where
         ReadTransaction: ReadTransactionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(index: YapDB.Index) -> ReadTransaction -> YapItem<Self, Metadata>? {
+        Metadata.Coder.Value == Metadata {
         return { $0.readWithMetadataAtIndex(index) }
     }
 
@@ -40,13 +40,13 @@ extension Persistable where
     - returns: a (ReadTransaction) -> [Self] closure.
     */
     public static func readWithMetadataAtIndexes<
-        Indexes, ReadTransaction, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, ReadTransaction, Metadata>(_ indexes: Indexes) -> (ReadTransaction) -> [YapItem<Self, Metadata>?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         ReadTransaction: ReadTransactionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(indexes: Indexes) -> ReadTransaction -> [YapItem<Self, Metadata>] {
+        Metadata.Coder.Value == Metadata {
         return { $0.readWithMetadataAtIndexes(indexes) }
     }
 
@@ -58,11 +58,11 @@ extension Persistable where
     - returns: a (ReadTransaction) -> Self? closure.
     */
     public static func readWithMetadataByKey<
-        ReadTransaction, Metadata where
+        ReadTransaction, Metadata>(_ key: String) -> (ReadTransaction) -> YapItem<Self, Metadata>? where
         ReadTransaction: ReadTransactionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(key: String) -> ReadTransaction -> YapItem<Self, Metadata>? {
+        Metadata.Coder.Value == Metadata {
         return { $0.readWithMetadataByKey(key) }
     }
 
@@ -74,13 +74,13 @@ extension Persistable where
     - returns: a (ReadTransaction) -> [Self] closure.
     */
     public static func readWithMetadataByKeys<
-        Keys, ReadTransaction, Metadata where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
+        Keys, ReadTransaction, Metadata>(_ keys: Keys) -> (ReadTransaction) -> [YapItem<Self, Metadata>?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
         ReadTransaction: ReadTransactionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(keys: Keys) -> ReadTransaction -> [YapItem<Self, Metadata>] {
+        Metadata.Coder.Value == Metadata {
         return  { $0.readWithMetadataAtIndexes(Self.indexesWithKeys(keys)) }
     }
 
@@ -92,11 +92,11 @@ extension Persistable where
     - returns: a (WriteTransaction) -> Self closure
     */
     public func writeWithMetadata<
-        WriteTransaction, Metadata where
+        WriteTransaction, Metadata>(_ metadata: Metadata? = nil) -> (WriteTransaction) -> YapItem<Self, Metadata> where
         WriteTransaction: WriteTransactionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(metadata: Metadata? = nil) -> WriteTransaction -> YapItem<Self, Metadata> {
+        Metadata.Coder.Value == Metadata {
         return { $0.writeWithMetadata(YapItem(self, metadata)) }
     }
 }
diff --git a/Sources/Functional_AnyWithObjectMetadata.swift b/Sources/Functional_AnyWithObjectMetadata.swift
index 1b905b4..367ef22 100644
--- a/Sources/Functional_AnyWithObjectMetadata.swift
+++ b/Sources/Functional_AnyWithObjectMetadata.swift
@@ -21,7 +21,7 @@ extension ReadTransactionType {
     - returns: an optional `MetadataType`
     */
     public func readMetadataAtIndex<
-        MetadataType: NSCoding>(index: YapDB.Index) -> MetadataType? {
+        MetadataType: NSCoding>(_ index: YapDB.Index) -> MetadataType? {
             return readMetadataAtIndex(index) as? MetadataType
     }
 
@@ -32,11 +32,11 @@ extension ReadTransactionType {
     - returns: an array of `MetadataType`
     */
     public func readMetadataAtIndexes<
-        Indexes, MetadataType where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
-        MetadataType: NSCoding>(indexes: Indexes) -> [MetadataType] {
-            return indexes.flatMap(readMetadataAtIndex)
+        Indexes, MetadataType>(_ indexes: Indexes) -> [MetadataType?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
+        MetadataType: NSCoding {
+            return indexes.map(readMetadataAtIndex)
     }
 }
 
@@ -49,7 +49,7 @@ extension ConnectionType {
     - returns: an optional `MetadataType`
     */
     public func readMetadataAtIndex<
-        MetadataType: NSCoding>(index: YapDB.Index) -> MetadataType? {
+        MetadataType: NSCoding>(_ index: YapDB.Index) -> MetadataType? {
             return read { $0.readMetadataAtIndex(index) }
     }
 
@@ -60,10 +60,10 @@ extension ConnectionType {
     - returns: an array of `MetadataType`
     */
     public func readMetadataAtIndexes<
-        Indexes, MetadataType where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
-        MetadataType: NSCoding>(indexes: Indexes) -> [MetadataType] {
+        Indexes, MetadataType>(_ indexes: Indexes) -> [MetadataType?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
+        MetadataType: NSCoding {
             return read { $0.readMetadataAtIndexes(indexes) }
     }
 }
diff --git a/Sources/Functional_AnyWithValueMetadata.swift b/Sources/Functional_AnyWithValueMetadata.swift
index 1e91339..fe210ef 100644
--- a/Sources/Functional_AnyWithValueMetadata.swift
+++ b/Sources/Functional_AnyWithValueMetadata.swift
@@ -21,11 +21,11 @@ extension ReadTransactionType {
     - returns: an optional `MetadataType`
     */
     public func readMetadataAtIndex<
-        MetadataType where
+        MetadataType>(_ index: YapDB.Index) -> MetadataType? where
         MetadataType: ValueCoding,
         MetadataType.Coder: NSCoding,
-        MetadataType.Coder.ValueType == MetadataType>(index: YapDB.Index) -> MetadataType? {
-            return MetadataType.decode(readMetadataAtIndex(index))
+        MetadataType.Coder.Value == MetadataType {
+            return MetadataType.decode(readMetadataAtIndex(index) as Any?)
     }
 
     /**
@@ -35,13 +35,13 @@ extension ReadTransactionType {
     - returns: an array of `MetadataType`
     */
     public func readMetadataAtIndexes<
-        Indexes, MetadataType where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, MetadataType>(_ indexes: Indexes) -> [MetadataType?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         MetadataType: ValueCoding,
         MetadataType.Coder: NSCoding,
-        MetadataType.Coder.ValueType == MetadataType>(indexes: Indexes) -> [MetadataType] {
-            return indexes.flatMap(readMetadataAtIndex)
+        MetadataType.Coder.Value == MetadataType {
+            return indexes.map(readMetadataAtIndex)
     }
 }
 
@@ -54,10 +54,10 @@ extension ConnectionType {
     - returns: an optional `MetadataType`
     */
     public func readMetadataAtIndex<
-        MetadataType where
+        MetadataType>(_ index: YapDB.Index) -> MetadataType? where
         MetadataType: ValueCoding,
         MetadataType.Coder: NSCoding,
-        MetadataType.Coder.ValueType == MetadataType>(index: YapDB.Index) -> MetadataType? {
+        MetadataType.Coder.Value == MetadataType {
             return read { $0.readMetadataAtIndex(index) }
     }
 
@@ -68,12 +68,12 @@ extension ConnectionType {
     - returns: an array of `MetadataType`
     */
     public func readMetadataAtIndexes<
-        Indexes, MetadataType where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, MetadataType>(_ indexes: Indexes) -> [MetadataType?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         MetadataType: ValueCoding,
         MetadataType.Coder: NSCoding,
-        MetadataType.Coder.ValueType == MetadataType>(indexes: Indexes) -> [MetadataType] {
+        MetadataType.Coder.Value == MetadataType {
             return read { $0.readMetadataAtIndexes(indexes) }
     }
 }
diff --git a/Sources/Functional_ObjectWithNoMetadata.swift b/Sources/Functional_ObjectWithNoMetadata.swift
index 6cebd10..f67317a 100644
--- a/Sources/Functional_ObjectWithNoMetadata.swift
+++ b/Sources/Functional_ObjectWithNoMetadata.swift
@@ -21,9 +21,9 @@ extension ReadTransactionType {
     - returns: an optional `ItemType`
     */
     public func readAtIndex<
-        Object where
+        Object>(_ index: YapDB.Index) -> Object? where
         Object: Persistable,
-        Object: NSCoding>(index: YapDB.Index) -> Object? {
+        Object: NSCoding {
             return readAtIndex(index) as? Object
     }
 
@@ -34,12 +34,12 @@ extension ReadTransactionType {
     - returns: an array of `ItemType`
     */
     public func readAtIndexes<
-        Indexes, Object where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, Object>(_ indexes: Indexes) -> [Object?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         Object: Persistable,
-        Object: NSCoding>(indexes: Indexes) -> [Object] {
-            return indexes.flatMap(readAtIndex)
+        Object: NSCoding {
+            return indexes.map(readAtIndex)
     }
 
     /**
@@ -49,9 +49,9 @@ extension ReadTransactionType {
     - returns: an optional `ItemType`
     */
     public func readByKey<
-        Object where
+        Object>(_ key: String) -> Object? where
         Object: Persistable,
-        Object: NSCoding>(key: String) -> Object? {
+        Object: NSCoding {
             return readAtIndex(Object.indexWithKey(key))
     }
 
@@ -62,11 +62,11 @@ extension ReadTransactionType {
     - returns: an array of `ItemType`
     */
     public func readByKeys<
-        Keys, Object where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
+        Keys, Object>(_ keys: Keys) -> [Object?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
         Object: Persistable,
-        Object: NSCoding>(keys: Keys) -> [Object] {
+        Object: NSCoding {
             return readAtIndexes(Object.indexesWithKeys(keys))
     }
 
@@ -76,9 +76,9 @@ extension ReadTransactionType {
     - returns: an array of `ItemType`
     */
     public func readAll<
-        Object where
+        Object>() -> [Object?] where
         Object: Persistable,
-        Object: NSCoding>() -> [Object] {
+        Object: NSCoding {
             return readByKeys(keysInCollection(Object.collection))
     }
 }
@@ -92,9 +92,9 @@ extension ConnectionType {
     - returns: an optional `ItemType`
     */
     public func readAtIndex<
-        Object where
+        Object>(_ index: YapDB.Index) -> Object? where
         Object: Persistable,
-        Object: NSCoding>(index: YapDB.Index) -> Object? {
+        Object: NSCoding {
             return read { $0.readAtIndex(index) }
     }
 
@@ -105,11 +105,11 @@ extension ConnectionType {
     - returns: an array of `ItemType`
     */
     public func readAtIndexes<
-        Indexes, Object where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, Object>(_ indexes: Indexes) -> [Object?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         Object: Persistable,
-        Object: NSCoding>(indexes: Indexes) -> [Object] {
+        Object: NSCoding {
             return read { $0.readAtIndexes(indexes) }
     }
 
@@ -120,9 +120,9 @@ extension ConnectionType {
     - returns: an optional `ItemType`
     */
     public func readByKey<
-        Object where
+        Object>(_ key: String) -> Object? where
         Object: Persistable,
-        Object: NSCoding>(key: String) -> Object? {
+        Object: NSCoding {
             return readAtIndex(Object.indexWithKey(key))
     }
 
@@ -133,11 +133,11 @@ extension ConnectionType {
     - returns: an array of `ItemType`
     */
     public func readByKeys<
-        Keys, Object where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
+        Keys, Object>(_ keys: Keys) -> [Object?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
         Object: Persistable,
-        Object: NSCoding>(keys: Keys) -> [Object] {
+        Object: NSCoding {
             return readAtIndexes(Object.indexesWithKeys(keys))
     }
 
@@ -147,9 +147,9 @@ extension ConnectionType {
     - returns: an array of `ItemType`
     */
     public func readAll<
-        Object where
+        Object>() -> [Object?] where
         Object: Persistable,
-        Object: NSCoding>() -> [Object] {
+        Object: NSCoding {
             return read { $0.readAll() }
     }
 }
@@ -165,10 +165,10 @@ extension WriteTransactionType {
     - returns: the same item
     */
     public func write<
-        Object where
+        Object>(_ item: Object) -> Object where
         Object: Persistable,
-        Object: NSCoding>(item: Object) -> Object {
-            writeAtIndex(item.index, object: item, metadata: .None)
+        Object: NSCoding {
+            writeAtIndex(item.index, object: item, metadata: .none)
             return item
     }
 
@@ -179,11 +179,11 @@ extension WriteTransactionType {
     - returns: the same items, in an array.
     */
     public func write<
-        Items, Object where
-        Items: SequenceType,
-        Items.Generator.Element == Object,
+        Items, Object>(_ items: Items) -> [Object] where
+        Items: Sequence,
+        Items.Iterator.Element == Object,
         Object: Persistable,
-        Object: NSCoding>(items: Items) -> [Object] {
+        Object: NSCoding {
             return items.map(write)
     }
 }
@@ -197,9 +197,9 @@ extension ConnectionType {
     - returns: the same item
     */
     public func write<
-        Object where
+        Object>(_ item: Object) -> Object where
         Object: Persistable,
-        Object: NSCoding>(item: Object) -> Object {
+        Object: NSCoding {
             return write { $0.write(item) }
     }
 
@@ -210,11 +210,11 @@ extension ConnectionType {
     - returns: the same items, in an array.
     */
     public func write<
-        Items, Object where
-        Items: SequenceType,
-        Items.Generator.Element == Object,
+        Items, Object>(_ items: Items) -> [Object] where
+        Items: Sequence,
+        Items.Iterator.Element == Object,
         Object: Persistable,
-        Object: NSCoding>(items: Items) -> [Object] {
+        Object: NSCoding {
             return write { $0.write(items) }
     }
 
@@ -226,9 +226,9 @@ extension ConnectionType {
     - parameter completion: a dispatch_block_t for completion.
     */
     public func asyncWrite<
-        Object where
+        Object>(_ item: Object, queue: DispatchQueue = DispatchQueue.main, completion: ((Object) -> Void)? = .none) where
         Object: Persistable,
-        Object: NSCoding>(item: Object, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: (Object -> Void)? = .None) {
+        Object: NSCoding {
             asyncWrite({ $0.write(item) }, queue: queue, completion: completion)
     }
 
@@ -240,11 +240,11 @@ extension ConnectionType {
     - parameter completion: a dispatch_block_t for completion.
     */
     public func asyncWrite<
-        Items, Object where
-        Items: SequenceType,
-        Items.Generator.Element == Object,
+        Items, Object>(_ items: Items, queue: DispatchQueue = DispatchQueue.main, completion: (([Object]) -> Void)? = .none) where
+        Items: Sequence,
+        Items.Iterator.Element == Object,
         Object: Persistable,
-        Object: NSCoding>(items: Items, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: ([Object] -> Void)? = .None) {
+        Object: NSCoding {
             asyncWrite({ $0.write(items) }, queue: queue, completion: completion)
     }
 }
diff --git a/Sources/Functional_ObjectWithObjectMetadata.swift b/Sources/Functional_ObjectWithObjectMetadata.swift
index 3a9d98d..70e2d60 100644
--- a/Sources/Functional_ObjectWithObjectMetadata.swift
+++ b/Sources/Functional_ObjectWithObjectMetadata.swift
@@ -21,10 +21,10 @@ extension ReadTransactionType {
     - returns: an optional `ItemType`
     */
     public func readWithMetadataAtIndex<
-        Object, Metadata where
+        Object, Metadata>(_ index: YapDB.Index) -> YapItem<Object, Metadata>? where
         Object: Persistable,
         Object: NSCoding,
-        Metadata: NSCoding>(index: YapDB.Index) -> YapItem<Object, Metadata>? {
+        Metadata: NSCoding {
             guard let item: Object = readAtIndex(index) else { return nil }
             let metadata: Metadata? = readMetadataAtIndex(index)
             return YapItem(item, metadata)
@@ -37,14 +37,13 @@ extension ReadTransactionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataAtIndexes<
-        Indexes, Object, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, Object, Metadata>(_ indexes: Indexes) -> [YapItem<Object, Metadata>?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         Object: Persistable,
         Object: NSCoding,
-        Metadata: NSCoding>(indexes: Indexes) -> [YapItem<Object, Metadata>] {
-            // FIXME: using flatMap means the output length need not match the input length
-            return indexes.flatMap(readWithMetadataAtIndex)
+        Metadata: NSCoding {
+            return indexes.map(readWithMetadataAtIndex)
     }
 
     /**
@@ -54,10 +53,10 @@ extension ReadTransactionType {
     - returns: an optional `ItemType`
     */
     public func readWithMetadataByKey<
-        Object, Metadata where
+        Object, Metadata>(_ key: String) -> YapItem<Object, Metadata>? where
         Object: Persistable,
         Object: NSCoding,
-        Metadata: NSCoding>(key: String) -> YapItem<Object, Metadata>? {
+        Metadata: NSCoding {
             return readWithMetadataAtIndex(Object.indexWithKey(key))
     }
 
@@ -68,12 +67,12 @@ extension ReadTransactionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataByKeys<
-        Keys, Object, Metadata where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
+        Keys, Object, Metadata>(_ keys: Keys) -> [YapItem<Object, Metadata>?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
         Object: Persistable,
         Object: NSCoding,
-        Metadata: NSCoding>(keys: Keys) -> [YapItem<Object, Metadata>] {
+        Metadata: NSCoding {
             return readWithMetadataAtIndexes(Object.indexesWithKeys(keys))
     }
 
@@ -83,10 +82,10 @@ extension ReadTransactionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataAll<
-        Object, Metadata where
+        Object, Metadata>() -> [YapItem<Object, Metadata>?] where
         Object: Persistable,
         Object: NSCoding,
-        Metadata: NSCoding>() -> [YapItem<Object, Metadata>] {
+        Metadata: NSCoding {
             return readWithMetadataByKeys(keysInCollection(Object.collection))
     }
 }
@@ -100,10 +99,10 @@ extension ConnectionType {
     - returns: an optional `ItemType`
     */
     public func readWithMetadataAtIndex<
-        Object, Metadata where
+        Object, Metadata>(_ index: YapDB.Index) -> YapItem<Object, Metadata>? where
         Object: Persistable,
         Object: NSCoding,
-        Metadata: NSCoding>(index: YapDB.Index) -> YapItem<Object, Metadata>? {
+        Metadata: NSCoding {
             return read { $0.readWithMetadataAtIndex(index) }
     }
 
@@ -114,12 +113,12 @@ extension ConnectionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataAtIndexes<
-        Indexes, Object, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, Object, Metadata>(_ indexes: Indexes) -> [YapItem<Object, Metadata>?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         Object: Persistable,
         Object: NSCoding,
-        Metadata: NSCoding>(indexes: Indexes) -> [YapItem<Object, Metadata>] {
+        Metadata: NSCoding {
             return read { $0.readWithMetadataAtIndexes(indexes) }
     }
 
@@ -130,10 +129,10 @@ extension ConnectionType {
     - returns: an optional `ItemType`
     */
     public func readWithMetadataByKey<
-        Object, Metadata where
+        Object, Metadata>(_ key: String) -> YapItem<Object, Metadata>? where
         Object: Persistable,
         Object: NSCoding,
-        Metadata: NSCoding>(key: String) -> YapItem<Object, Metadata>? {
+        Metadata: NSCoding {
             return readWithMetadataAtIndex(Object.indexWithKey(key))
     }
 
@@ -144,12 +143,12 @@ extension ConnectionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataByKeys<
-        Keys, Object, Metadata where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
+        Keys, Object, Metadata>(_ keys: Keys) -> [YapItem<Object, Metadata>?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
         Object: Persistable,
         Object: NSCoding,
-        Metadata: NSCoding>(keys: Keys) -> [YapItem<Object, Metadata>] {
+        Metadata: NSCoding {
             return readWithMetadataAtIndexes(Object.indexesWithKeys(keys))
     }
 
@@ -159,10 +158,10 @@ extension ConnectionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataAll<
-        Object, Metadata where
+        Object, Metadata>() -> [YapItem<Object, Metadata>?] where
         Object: Persistable,
         Object: NSCoding,
-        Metadata: NSCoding>() -> [YapItem<Object, Metadata>] {
+        Metadata: NSCoding {
             return read { $0.readWithMetadataAll() }
     }
 }
@@ -177,10 +176,10 @@ extension WriteTransactionType {
     - parameter item: the item to store.
     */
     public func writeWithMetadata<
-        Object, Metadata where
+        Object, Metadata>(_ item: YapItem<Object, Metadata>) -> YapItem<Object, Metadata> where
         Object: Persistable,
         Object: NSCoding,
-        Metadata: NSCoding>(item: YapItem<Object, Metadata>) -> YapItem<Object, Metadata> {
+        Metadata: NSCoding {
             writeAtIndex(item.value.index, object: item.value, metadata: item.metadata)
             return item
     }
@@ -191,12 +190,12 @@ extension WriteTransactionType {
     - parameter items: a SequenceType of items to store.
     */
     public func writeWithMetadata<
-        Items, Object, Metadata where
-        Items: SequenceType,
-        Items.Generator.Element == YapItem<Object, Metadata>,
+        Items, Object, Metadata>(_ items: Items) -> [YapItem<Object, Metadata>] where
+        Items: Sequence,
+        Items.Iterator.Element == YapItem<Object, Metadata>,
         Object: Persistable,
         Object: NSCoding,
-        Metadata: NSCoding>(items: Items) -> [YapItem<Object, Metadata>] {
+        Metadata: NSCoding {
             return items.map(writeWithMetadata)
     }
 }
@@ -209,10 +208,10 @@ extension ConnectionType {
     - parameter item: the item to store.
     */
     public func writeWithMetadata<
-        Object, Metadata where
+        Object, Metadata>(_ item: YapItem<Object, Metadata>) -> YapItem<Object, Metadata> where
         Object: Persistable,
         Object: NSCoding,
-        Metadata: NSCoding>(item: YapItem<Object, Metadata>) -> YapItem<Object, Metadata> {
+        Metadata: NSCoding {
             return write { $0.writeWithMetadata(item) }
     }
 
@@ -222,12 +221,12 @@ extension ConnectionType {
     - parameter items: a SequenceType of items to store.
     */
     public func writeWithMetadata<
-        Items, Object, Metadata where
-        Items: SequenceType,
-        Items.Generator.Element == YapItem<Object, Metadata>,
+        Items, Object, Metadata>(_ items: Items) -> [YapItem<Object, Metadata>] where
+        Items: Sequence,
+        Items.Iterator.Element == YapItem<Object, Metadata>,
         Object: Persistable,
         Object: NSCoding,
-        Metadata: NSCoding>(items: Items) -> [YapItem<Object, Metadata>] {
+        Metadata: NSCoding {
             return write { $0.writeWithMetadata(items) }
     }
 
@@ -239,10 +238,10 @@ extension ConnectionType {
     - parameter completion: a dispatch_block_t for completion.
     */
     public func asyncWriteWithMetadata<
-        Object, Metadata where
+        Object, Metadata>(_ item: YapItem<Object, Metadata>, queue: DispatchQueue = DispatchQueue.main, completion: ((YapItem<Object, Metadata>) -> Void)? = .none) where
         Object: Persistable,
         Object: NSCoding,
-        Metadata: NSCoding>(item: YapItem<Object, Metadata>, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: (YapItem<Object, Metadata> -> Void)? = .None) {
+        Metadata: NSCoding {
             asyncWrite({ $0.writeWithMetadata(item) }, queue: queue, completion: completion)
     }
 
@@ -254,12 +253,12 @@ extension ConnectionType {
     - parameter completion: a dispatch_block_t for completion.
     */
     public func asyncWriteWithMetadata<
-        Items, Object, Metadata where
-        Items: SequenceType,
-        Items.Generator.Element == YapItem<Object, Metadata>,
+        Items, Object, Metadata>(_ items: Items, queue: DispatchQueue = DispatchQueue.main, completion: (([YapItem<Object, Metadata>]) -> Void)? = .none) where
+        Items: Sequence,
+        Items.Iterator.Element == YapItem<Object, Metadata>,
         Object: Persistable,
         Object: NSCoding,
-        Metadata: NSCoding>(items: Items, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: ([YapItem<Object, Metadata>] -> Void)? = .None) {
+        Metadata: NSCoding {
             asyncWrite({ $0.writeWithMetadata(items) }, queue: queue, completion: completion)
     }
 }
diff --git a/Sources/Functional_ObjectWithValueMetadata.swift b/Sources/Functional_ObjectWithValueMetadata.swift
index ca78eb5..8c9906c 100644
--- a/Sources/Functional_ObjectWithValueMetadata.swift
+++ b/Sources/Functional_ObjectWithValueMetadata.swift
@@ -21,12 +21,12 @@ extension ReadTransactionType {
     - returns: an optional `ItemType`
     */
     public func readWithMetadataAtIndex<
-        Object, Metadata where
+        Object, Metadata>(_ index: YapDB.Index) -> YapItem<Object, Metadata>? where
         Object: Persistable,
         Object: NSCoding,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(index: YapDB.Index) -> YapItem<Object, Metadata>? {
+        Metadata.Coder.Value == Metadata {
             guard let item: Object = readAtIndex(index) else { return nil }
             let metadata: Metadata? = readMetadataAtIndex(index)
             return YapItem(item, metadata)
@@ -39,16 +39,15 @@ extension ReadTransactionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataAtIndexes<
-        Indexes, Object, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, Object, Metadata>(_ indexes: Indexes) -> [YapItem<Object, Metadata>?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         Object: Persistable,
         Object: NSCoding,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(indexes: Indexes) -> [YapItem<Object, Metadata>] {
-            // FIXME: using flatMap means the output length need not match the input length
-            return indexes.flatMap(readWithMetadataAtIndex)
+        Metadata.Coder.Value == Metadata {
+            return indexes.map(readWithMetadataAtIndex)
     }
 
     /**
@@ -58,12 +57,12 @@ extension ReadTransactionType {
     - returns: an optional `ItemType`
     */
     public func readWithMetadataByKey<
-        Object, Metadata where
+        Object, Metadata>(_ key: String) -> YapItem<Object, Metadata>? where
         Object: Persistable,
         Object: NSCoding,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(key: String) -> YapItem<Object, Metadata>? {
+        Metadata.Coder.Value == Metadata {
             return readWithMetadataAtIndex(Object.indexWithKey(key))
     }
 
@@ -74,14 +73,14 @@ extension ReadTransactionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataByKeys<
-        Keys, Object, Metadata where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
+        Keys, Object, Metadata>(_ keys: Keys) -> [YapItem<Object, Metadata>?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
         Object: Persistable,
         Object: NSCoding,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(keys: Keys) -> [YapItem<Object, Metadata>] {
+        Metadata.Coder.Value == Metadata {
             return readWithMetadataAtIndexes(Object.indexesWithKeys(keys))
     }
 
@@ -91,12 +90,12 @@ extension ReadTransactionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataAll<
-        Object, Metadata where
+        Object, Metadata>() -> [YapItem<Object, Metadata>?] where
         Object: Persistable,
         Object: NSCoding,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>() -> [YapItem<Object, Metadata>] {
+        Metadata.Coder.Value == Metadata {
             return readWithMetadataByKeys(keysInCollection(Object.collection))
     }
 }
@@ -110,12 +109,12 @@ extension ConnectionType {
     - returns: an optional `ItemType`
     */
     public func readWithMetadataAtIndex<
-        Object, Metadata where
+        Object, Metadata>(_ index: YapDB.Index) -> YapItem<Object, Metadata>? where
         Object: Persistable,
         Object: NSCoding,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(index: YapDB.Index) -> YapItem<Object, Metadata>? {
+        Metadata.Coder.Value == Metadata {
             return read { $0.readWithMetadataAtIndex(index) }
     }
 
@@ -126,14 +125,14 @@ extension ConnectionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataAtIndexes<
-        Indexes, Object, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, Object, Metadata>(_ indexes: Indexes) -> [YapItem<Object, Metadata>?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         Object: Persistable,
         Object: NSCoding,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(indexes: Indexes) -> [YapItem<Object, Metadata>] {
+        Metadata.Coder.Value == Metadata {
             return read { $0.readWithMetadataAtIndexes(indexes) }
     }
 
@@ -144,12 +143,12 @@ extension ConnectionType {
     - returns: an optional `ItemType`
     */
     public func readWithMetadataByKey<
-        Object, Metadata where
+        Object, Metadata>(_ key: String) -> YapItem<Object, Metadata>? where
         Object: Persistable,
         Object: NSCoding,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(key: String) -> YapItem<Object, Metadata>? {
+        Metadata.Coder.Value == Metadata {
             return readWithMetadataAtIndex(Object.indexWithKey(key))
     }
 
@@ -160,14 +159,14 @@ extension ConnectionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataByKeys<
-        Keys, Object, Metadata where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
+        Keys, Object, Metadata>(_ keys: Keys) -> [YapItem<Object, Metadata>?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
         Object: Persistable,
         Object: NSCoding,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(keys: Keys) -> [YapItem<Object, Metadata>] {
+        Metadata.Coder.Value == Metadata {
             return readWithMetadataAtIndexes(Object.indexesWithKeys(keys))
     }
 
@@ -177,12 +176,12 @@ extension ConnectionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataAll<
-        Object, Metadata where
+        Object, Metadata>() -> [YapItem<Object, Metadata>?] where
         Object: Persistable,
         Object: NSCoding,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>() -> [YapItem<Object, Metadata>] {
+        Metadata.Coder.Value == Metadata {
             return read { $0.readWithMetadataAll() }
     }
 }
@@ -197,12 +196,12 @@ extension WriteTransactionType {
     - parameter item: the item to store.
     */
     public func writeWithMetadata<
-        Object, Metadata where
+        Object, Metadata>(_ item: YapItem<Object, Metadata>) -> YapItem<Object, Metadata> where
         Object: Persistable,
         Object: NSCoding,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(item: YapItem<Object, Metadata>) -> YapItem<Object, Metadata> {
+        Metadata.Coder.Value == Metadata {
             writeAtIndex(item.value.index, object: item.value, metadata: item.metadata?.encoded)
             return item
     }
@@ -213,14 +212,14 @@ extension WriteTransactionType {
     - parameter items: a SequenceType of items to store.
     */
     public func writeWithMetadata<
-        Items, Object, Metadata where
-        Items: SequenceType,
-        Items.Generator.Element == YapItem<Object, Metadata>,
+        Items, Object, Metadata>(_ items: Items) -> [YapItem<Object, Metadata>] where
+        Items: Sequence,
+        Items.Iterator.Element == YapItem<Object, Metadata>,
         Object: Persistable,
         Object: NSCoding,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(items: Items) -> [YapItem<Object, Metadata>] {
+        Metadata.Coder.Value == Metadata {
             return items.map(writeWithMetadata)
     }
 }
@@ -233,12 +232,12 @@ extension ConnectionType {
     - parameter item: the item to store.
     */
     public func writeWithMetadata<
-        Object, Metadata where
+        Object, Metadata>(_ item: YapItem<Object, Metadata>) -> YapItem<Object, Metadata> where
         Object: Persistable,
         Object: NSCoding,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(item: YapItem<Object, Metadata>) -> YapItem<Object, Metadata> {
+        Metadata.Coder.Value == Metadata {
             return write { $0.writeWithMetadata(item) }
     }
 
@@ -248,14 +247,14 @@ extension ConnectionType {
     - parameter items: a SequenceType of items to store.
     */
     public func writeWithMetadata<
-        Items, Object, Metadata where
-        Items: SequenceType,
-        Items.Generator.Element == YapItem<Object, Metadata>,
+        Items, Object, Metadata>(_ items: Items) -> [YapItem<Object, Metadata>] where
+        Items: Sequence,
+        Items.Iterator.Element == YapItem<Object, Metadata>,
         Object: Persistable,
         Object: NSCoding,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(items: Items) -> [YapItem<Object, Metadata>] {
+        Metadata.Coder.Value == Metadata {
             return write { $0.writeWithMetadata(items) }
     }
 
@@ -267,12 +266,12 @@ extension ConnectionType {
     - parameter completion: a dispatch_block_t for completion.
     */
     public func asyncWriteWithMetadata<
-        Object, Metadata where
+        Object, Metadata>(_ item: YapItem<Object, Metadata>, queue: DispatchQueue = DispatchQueue.main, completion: ((YapItem<Object, Metadata>) -> Void)? = .none) where
         Object: Persistable,
         Object: NSCoding,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(item: YapItem<Object, Metadata>, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: (YapItem<Object, Metadata> -> Void)? = .None) {
+        Metadata.Coder.Value == Metadata {
             asyncWrite({ $0.writeWithMetadata(item) }, queue: queue, completion: completion)
     }
 
@@ -284,14 +283,14 @@ extension ConnectionType {
     - parameter completion: a dispatch_block_t for completion.
     */
     public func asyncWriteWithMetadata<
-        Items, Object, Metadata where
-        Items: SequenceType,
-        Items.Generator.Element == YapItem<Object, Metadata>,
+        Items, Object, Metadata>(_ items: Items, queue: DispatchQueue = DispatchQueue.main, completion: (([YapItem<Object, Metadata>]) -> Void)? = .none) where
+        Items: Sequence,
+        Items.Iterator.Element == YapItem<Object, Metadata>,
         Object: Persistable,
         Object: NSCoding,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(items: Items, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: ([YapItem<Object, Metadata>] -> Void)? = .None) {
+        Metadata.Coder.Value == Metadata {
             asyncWrite({ $0.writeWithMetadata(items) }, queue: queue, completion: completion)
     }
 }
diff --git a/Sources/Functional_Remove.swift b/Sources/Functional_Remove.swift
index b45fc28..7074c6e 100644
--- a/Sources/Functional_Remove.swift
+++ b/Sources/Functional_Remove.swift
@@ -15,7 +15,7 @@ extension WriteTransactionType {
     
     - parameter item: a `Persistable` item
     */
-    public func remove<Item: Persistable>(item: Item) {
+    public func remove<Item: Persistable>(_ item: Item) {
         removeAtIndexes([item.index])
     }
 
@@ -25,10 +25,10 @@ extension WriteTransactionType {
     - parameter items: a sequence of `Persistable` items
     */
     public func remove<
-        Items, Item where
-        Items: SequenceType,
-        Items.Generator.Element == Item,
-        Item: Persistable>(items: Items) {
+        Items, Item>(_ items: Items) where
+        Items: Sequence,
+        Items.Iterator.Element == Item,
+        Item: Persistable {
             removeAtIndexes(items.map { $0.index })
     }
 }
@@ -41,7 +41,7 @@ extension ConnectionType {
 
     - parameter item: a `Persistable` item
     */
-    public func remove<Item: Persistable>(item: Item) {
+    public func remove<Item: Persistable>(_ item: Item) {
         write { $0.remove(item) }
     }
 
@@ -52,10 +52,10 @@ extension ConnectionType {
     - parameter items: a sequence of `Persistable` items
     */
     public func remove<
-        Items, Item where
-        Items: SequenceType,
-        Items.Generator.Element == Item,
-        Item: Persistable>(items: Items) {
+        Items, Item>(_ items: Items) where
+        Items: Sequence,
+        Items.Iterator.Element == Item,
+        Item: Persistable {
             write { $0.remove(items) }
     }
 
@@ -65,7 +65,7 @@ extension ConnectionType {
 
     - parameter item: a `Persistable` item
     */
-    public func asyncRemove<Item: Persistable>(item: Item, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: dispatch_block_t? = .None) {
+    public func asyncRemove<Item: Persistable>(_ item: Item, queue: DispatchQueue = DispatchQueue.main, completion: (()->())? = .none) {
         asyncWrite({ $0.remove(item) }, queue: queue, completion: { _ in completion?() })
     }
 
@@ -76,10 +76,10 @@ extension ConnectionType {
     - parameter items: a sequence of `Persistable` items
     */
     public func asyncRemove<
-        Items, Item where
-        Items: SequenceType,
-        Items.Generator.Element == Item,
-        Item: Persistable>(items: Items, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: dispatch_block_t? = .None) {
+        Items, Item>(_ items: Items, queue: DispatchQueue = DispatchQueue.main, completion: (()->())? = .none) where
+        Items: Sequence,
+        Items.Iterator.Element == Item,
+        Item: Persistable {
             asyncWrite({ $0.remove(items) }, queue: queue, completion: { _ in completion?() })
     }
 }
diff --git a/Sources/Functional_ValueWIthObjectMetadata.swift b/Sources/Functional_ValueWIthObjectMetadata.swift
index ce9f5b8..9e416fe 100644
--- a/Sources/Functional_ValueWIthObjectMetadata.swift
+++ b/Sources/Functional_ValueWIthObjectMetadata.swift
@@ -21,12 +21,12 @@ extension ReadTransactionType {
     - returns: an optional `ItemType`
     */
     public func readWithMetadataAtIndex<
-        Value, Metadata where
+        Value, Metadata>(_ index: YapDB.Index) -> YapItem<Value, Metadata>? where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
-        Metadata: NSCoding>(index: YapDB.Index) -> YapItem<Value, Metadata>? {
+        Value.Coder.Value == Value,
+        Metadata: NSCoding {
             guard let item: Value = Value.decode(readAtIndex(index)) else { return nil }
             let metadata: Metadata? = readMetadataAtIndex(index)
             return YapItem(item, metadata)
@@ -39,16 +39,15 @@ extension ReadTransactionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataAtIndexes<
-        Indexes, Value, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, Value, Metadata>(_ indexes: Indexes) -> [YapItem<Value, Metadata>?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
-        Metadata: NSCoding>(indexes: Indexes) -> [YapItem<Value, Metadata>] {
-            // FIXME: using flatMap means the output length need not match the input length
-            return indexes.flatMap(readWithMetadataAtIndex)
+        Value.Coder.Value == Value,
+        Metadata: NSCoding {
+            return indexes.map(readWithMetadataAtIndex)
     }
 
     /**
@@ -58,12 +57,12 @@ extension ReadTransactionType {
     - returns: an optional `ItemType`
     */
     public func readWithMetadataByKey<
-        Value, Metadata where
+        Value, Metadata>(_ key: String) -> YapItem<Value, Metadata>? where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
-        Metadata: NSCoding>(key: String) -> YapItem<Value, Metadata>? {
+        Value.Coder.Value == Value,
+        Metadata: NSCoding {
             return readWithMetadataAtIndex(Value.indexWithKey(key))
     }
 
@@ -74,14 +73,14 @@ extension ReadTransactionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataByKeys<
-        Keys, Value, Metadata where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
+        Keys, Value, Metadata>(_ keys: Keys) -> [YapItem<Value, Metadata>?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
-        Metadata: NSCoding>(keys: Keys) -> [YapItem<Value, Metadata>] {
+        Value.Coder.Value == Value,
+        Metadata: NSCoding {
             return readWithMetadataAtIndexes(Value.indexesWithKeys(keys))
     }
 
@@ -91,12 +90,12 @@ extension ReadTransactionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataAll<
-        Value, Metadata where
+        Value, Metadata>() -> [YapItem<Value, Metadata>?] where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
-        Metadata: NSCoding>() -> [YapItem<Value, Metadata>] {
+        Value.Coder.Value == Value,
+        Metadata: NSCoding {
             return readWithMetadataByKeys(keysInCollection(Value.collection))
     }
 }
@@ -110,12 +109,12 @@ extension ConnectionType {
     - returns: an optional `ItemType`
     */
     public func readWithMetadataAtIndex<
-        Value, Metadata where
+        Value, Metadata>(_ index: YapDB.Index) -> YapItem<Value, Metadata>? where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
-        Metadata: NSCoding>(index: YapDB.Index) -> YapItem<Value, Metadata>? {
+        Value.Coder.Value == Value,
+        Metadata: NSCoding {
             return read { $0.readWithMetadataAtIndex(index) }
     }
 
@@ -126,14 +125,14 @@ extension ConnectionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataAtIndexes<
-        Indexes, Value, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, Value, Metadata>(_ indexes: Indexes) -> [YapItem<Value, Metadata>?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
-        Metadata: NSCoding>(indexes: Indexes) -> [YapItem<Value, Metadata>] {
+        Value.Coder.Value == Value,
+        Metadata: NSCoding {
             return read { $0.readWithMetadataAtIndexes(indexes) }
     }
 
@@ -144,12 +143,12 @@ extension ConnectionType {
     - returns: an optional `ItemType`
     */
     public func readWithMetadataByKey<
-        Value, Metadata where
+        Value, Metadata>(_ key: String) -> YapItem<Value, Metadata>? where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
-        Metadata: NSCoding>(key: String) -> YapItem<Value, Metadata>? {
+        Value.Coder.Value == Value,
+        Metadata: NSCoding {
             return readWithMetadataAtIndex(Value.indexWithKey(key))
     }
 
@@ -160,14 +159,14 @@ extension ConnectionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataByKeys<
-        Keys, Value, Metadata where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
+        Keys, Value, Metadata>(_ keys: Keys) -> [YapItem<Value, Metadata>?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
-        Metadata: NSCoding>(keys: Keys) -> [YapItem<Value, Metadata>] {
+        Value.Coder.Value == Value,
+        Metadata: NSCoding {
             return readWithMetadataAtIndexes(Value.indexesWithKeys(keys))
     }
 
@@ -177,12 +176,12 @@ extension ConnectionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataAll<
-        Value, Metadata where
+        Value, Metadata>() -> [YapItem<Value, Metadata>?] where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
-        Metadata: NSCoding>() -> [YapItem<Value, Metadata>] {
+        Value.Coder.Value == Value,
+        Metadata: NSCoding {
             return read { $0.readWithMetadataAll() }
     }
 }
@@ -197,12 +196,12 @@ extension WriteTransactionType {
     - parameter item: the item to store.
     */
     public func writeWithMetadata<
-        Value, Metadata where
+        Value, Metadata>(_ item: YapItem<Value, Metadata>) -> YapItem<Value, Metadata> where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
-        Metadata: NSCoding>(item: YapItem<Value, Metadata>) -> YapItem<Value, Metadata> {
+        Value.Coder.Value == Value,
+        Metadata: NSCoding {
             writeAtIndex(item.value.index, object: item.value.encoded, metadata: item.metadata)
             return item
     }
@@ -213,14 +212,14 @@ extension WriteTransactionType {
     - parameter items: a SequenceType of items to store.
     */
     public func writeWithMetadata<
-        Items, Value, Metadata where
-        Items: SequenceType,
-        Items.Generator.Element == YapItem<Value, Metadata>,
+        Items, Value, Metadata>(_ items: Items) -> [YapItem<Value, Metadata>] where
+        Items: Sequence,
+        Items.Iterator.Element == YapItem<Value, Metadata>,
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
-        Metadata: NSCoding>(items: Items) -> [YapItem<Value, Metadata>] {
+        Value.Coder.Value == Value,
+        Metadata: NSCoding {
             return items.map(writeWithMetadata)
     }
 }
@@ -233,12 +232,12 @@ extension ConnectionType {
     - parameter item: the item to store.
     */
     public func writeWithMetadata<
-        Value, Metadata where
+        Value, Metadata>(_ item: YapItem<Value, Metadata>) -> YapItem<Value, Metadata> where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
-        Metadata: NSCoding>(item: YapItem<Value, Metadata>) -> YapItem<Value, Metadata> {
+        Value.Coder.Value == Value,
+        Metadata: NSCoding {
             return write { $0.writeWithMetadata(item) }
     }
 
@@ -248,14 +247,14 @@ extension ConnectionType {
     - parameter items: a SequenceType of items to store.
     */
     public func writeWithMetadata<
-        Items, Value, Metadata where
-        Items: SequenceType,
-        Items.Generator.Element == YapItem<Value, Metadata>,
+        Items, Value, Metadata>(_ items: Items) -> [YapItem<Value, Metadata>] where
+        Items: Sequence,
+        Items.Iterator.Element == YapItem<Value, Metadata>,
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
-        Metadata: NSCoding>(items: Items) -> [YapItem<Value, Metadata>] {
+        Value.Coder.Value == Value,
+        Metadata: NSCoding {
             return write { $0.writeWithMetadata(items) }
     }
 
@@ -267,12 +266,12 @@ extension ConnectionType {
     - parameter completion: a dispatch_block_t for completion.
     */
     public func asyncWriteWithMetadata<
-        Value, Metadata where
+        Value, Metadata>(_ item: YapItem<Value, Metadata>, queue: DispatchQueue = DispatchQueue.main, completion: ((YapItem<Value, Metadata>) -> Void)? = .none) where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
-        Metadata: NSCoding>(item: YapItem<Value, Metadata>, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: (YapItem<Value, Metadata> -> Void)? = .None) {
+        Value.Coder.Value == Value,
+        Metadata: NSCoding {
             asyncWrite({ $0.writeWithMetadata(item) }, queue: queue, completion: completion)
     }
 
@@ -284,14 +283,14 @@ extension ConnectionType {
     - parameter completion: a dispatch_block_t for completion.
     */
     public func asyncWriteWithMetadata<
-        Items, Value, Metadata where
-        Items: SequenceType,
-        Items.Generator.Element == YapItem<Value, Metadata>,
+        Items, Value, Metadata>(_ items: Items, queue: DispatchQueue = DispatchQueue.main, completion: (([YapItem<Value, Metadata>]) -> Void)? = .none) where
+        Items: Sequence,
+        Items.Iterator.Element == YapItem<Value, Metadata>,
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
-        Metadata: NSCoding>(items: Items, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: ([YapItem<Value, Metadata>] -> Void)? = .None) {
+        Value.Coder.Value == Value,
+        Metadata: NSCoding {
             asyncWrite({ $0.writeWithMetadata(items) }, queue: queue, completion: completion)
     }
 }
diff --git a/Sources/Functional_ValueWIthValueMetadata.swift b/Sources/Functional_ValueWIthValueMetadata.swift
index 19fb418..2147f6f 100644
--- a/Sources/Functional_ValueWIthValueMetadata.swift
+++ b/Sources/Functional_ValueWIthValueMetadata.swift
@@ -21,14 +21,14 @@ extension ReadTransactionType {
     - returns: an optional `ItemType`
     */
     public func readWithMetadataAtIndex<
-        Value, Metadata where
+        Value, Metadata>(_ index: YapDB.Index) -> YapItem<Value, Metadata>? where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
+        Value.Coder.Value == Value,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(index: YapDB.Index) -> YapItem<Value, Metadata>? {
+        Metadata.Coder.Value == Metadata {
             guard let item: Value = Value.decode(readAtIndex(index)) else { return nil }
             let metadata: Metadata? = readMetadataAtIndex(index)
             return YapItem(item, metadata)
@@ -41,18 +41,17 @@ extension ReadTransactionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataAtIndexes<
-        Indexes, Value, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, Value, Metadata>(_ indexes: Indexes) -> [YapItem<Value, Metadata>?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
+        Value.Coder.Value == Value,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(indexes: Indexes) -> [YapItem<Value, Metadata>] {
-            // FIXME: using flatMap means the output length need not match the input length
-            return indexes.flatMap(readWithMetadataAtIndex)
+        Metadata.Coder.Value == Metadata {
+            return indexes.map(readWithMetadataAtIndex)
     }
 
     /**
@@ -62,14 +61,14 @@ extension ReadTransactionType {
     - returns: an optional `ItemType`
     */
     public func readWithMetadataByKey<
-        Value, Metadata where
+        Value, Metadata>(_ key: String) -> YapItem<Value, Metadata>? where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
+        Value.Coder.Value == Value,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(key: String) -> YapItem<Value, Metadata>? {
+        Metadata.Coder.Value == Metadata {
             return readWithMetadataAtIndex(Value.indexWithKey(key))
     }
 
@@ -80,16 +79,16 @@ extension ReadTransactionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataByKeys<
-        Keys, Value, Metadata where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
+        Keys, Value, Metadata>(_ keys: Keys) -> [YapItem<Value, Metadata>?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
+        Value.Coder.Value == Value,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(keys: Keys) -> [YapItem<Value, Metadata>] {
+        Metadata.Coder.Value == Metadata {
             return readWithMetadataAtIndexes(Value.indexesWithKeys(keys))
     }
 
@@ -99,14 +98,14 @@ extension ReadTransactionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataAll<
-        Value, Metadata where
+        Value, Metadata>() -> [YapItem<Value, Metadata>?] where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
+        Value.Coder.Value == Value,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>() -> [YapItem<Value, Metadata>] {
+        Metadata.Coder.Value == Metadata {
             return readWithMetadataByKeys(keysInCollection(Value.collection))
     }
 }
@@ -120,14 +119,14 @@ extension ConnectionType {
     - returns: an optional `ItemType`
     */
     public func readWithMetadataAtIndex<
-        Value, Metadata where
+        Value, Metadata>(_ index: YapDB.Index) -> YapItem<Value, Metadata>? where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
+        Value.Coder.Value == Value,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(index: YapDB.Index) -> YapItem<Value, Metadata>? {
+        Metadata.Coder.Value == Metadata {
             return read { $0.readWithMetadataAtIndex(index) }
     }
 
@@ -138,16 +137,16 @@ extension ConnectionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataAtIndexes<
-        Indexes, Value, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, Value, Metadata>(_ indexes: Indexes) -> [YapItem<Value, Metadata>?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
+        Value.Coder.Value == Value,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(indexes: Indexes) -> [YapItem<Value, Metadata>] {
+        Metadata.Coder.Value == Metadata {
             return read { $0.readWithMetadataAtIndexes(indexes) }
     }
 
@@ -158,14 +157,14 @@ extension ConnectionType {
     - returns: an optional `ItemType`
     */
     public func readWithMetadataByKey<
-        Value, Metadata where
+        Value, Metadata>(_ key: String) -> YapItem<Value, Metadata>? where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
+        Value.Coder.Value == Value,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(key: String) -> YapItem<Value, Metadata>? {
+        Metadata.Coder.Value == Metadata {
             return readWithMetadataAtIndex(Value.indexWithKey(key))
     }
 
@@ -176,16 +175,16 @@ extension ConnectionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataByKeys<
-        Keys, Value, Metadata where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
+        Keys, Value, Metadata>(_ keys: Keys) -> [YapItem<Value, Metadata>?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
+        Value.Coder.Value == Value,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(keys: Keys) -> [YapItem<Value, Metadata>] {
+        Metadata.Coder.Value == Metadata {
             return readWithMetadataAtIndexes(Value.indexesWithKeys(keys))
     }
 
@@ -195,14 +194,14 @@ extension ConnectionType {
     - returns: an array of `ItemType`
     */
     public func readWithMetadataAll<
-        Value, Metadata where
+        Value, Metadata>() -> [YapItem<Value, Metadata>?] where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
+        Value.Coder.Value == Value,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>() -> [YapItem<Value, Metadata>] {
+        Metadata.Coder.Value == Metadata {
             return read { $0.readWithMetadataAll() }
     }
 }
@@ -217,14 +216,14 @@ extension WriteTransactionType {
     - parameter item: the item to store.
     */
     public func writeWithMetadata<
-        Value, Metadata where
+        Value, Metadata>(_ item: YapItem<Value, Metadata>) -> YapItem<Value, Metadata> where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
+        Value.Coder.Value == Value,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(item: YapItem<Value, Metadata>) -> YapItem<Value, Metadata> {
+        Metadata.Coder.Value == Metadata {
             writeAtIndex(item.value.index, object: item.value.encoded, metadata: item.metadata?.encoded)
             return item
     }
@@ -235,16 +234,16 @@ extension WriteTransactionType {
     - parameter items: a SequenceType of items to store.
     */
     public func writeWithMetadata<
-        Items, Value, Metadata where
-        Items: SequenceType,
-        Items.Generator.Element == YapItem<Value, Metadata>,
+        Items, Value, Metadata>(_ items: Items) -> [YapItem<Value, Metadata>] where
+        Items: Sequence,
+        Items.Iterator.Element == YapItem<Value, Metadata>,
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
+        Value.Coder.Value == Value,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(items: Items) -> [YapItem<Value, Metadata>] {
+        Metadata.Coder.Value == Metadata {
             return items.map(writeWithMetadata)
     }
 }
@@ -257,14 +256,14 @@ extension ConnectionType {
     - parameter item: the item to store.
     */
     public func writeWithMetadata<
-        Value, Metadata where
+        Value, Metadata>(_ item: YapItem<Value, Metadata>) -> YapItem<Value, Metadata> where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
+        Value.Coder.Value == Value,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(item: YapItem<Value, Metadata>) -> YapItem<Value, Metadata> {
+        Metadata.Coder.Value == Metadata {
             return write { $0.writeWithMetadata(item) }
     }
 
@@ -274,16 +273,16 @@ extension ConnectionType {
     - parameter items: a SequenceType of items to store.
     */
     public func writeWithMetadata<
-        Items, Value, Metadata where
-        Items: SequenceType,
-        Items.Generator.Element == YapItem<Value, Metadata>,
+        Items, Value, Metadata>(_ items: Items) -> [YapItem<Value, Metadata>] where
+        Items: Sequence,
+        Items.Iterator.Element == YapItem<Value, Metadata>,
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
+        Value.Coder.Value == Value,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(items: Items) -> [YapItem<Value, Metadata>] {
+        Metadata.Coder.Value == Metadata {
             return write { $0.writeWithMetadata(items) }
     }
 
@@ -295,14 +294,14 @@ extension ConnectionType {
     - parameter completion: a dispatch_block_t for completion.
     */
     public func asyncWriteWithMetadata<
-        Value, Metadata where
+        Value, Metadata>(_ item: YapItem<Value, Metadata>, queue: DispatchQueue = DispatchQueue.main, completion: ((YapItem<Value, Metadata>) -> Void)? = .none) where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
+        Value.Coder.Value == Value,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(item: YapItem<Value, Metadata>, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: (YapItem<Value, Metadata> -> Void)? = .None) {
+        Metadata.Coder.Value == Metadata {
             asyncWrite({ $0.writeWithMetadata(item) }, queue: queue, completion: completion)
     }
 
@@ -314,16 +313,16 @@ extension ConnectionType {
     - parameter completion: a dispatch_block_t for completion.
     */
     public func asyncWriteWithMetadata<
-        Items, Value, Metadata where
-        Items: SequenceType,
-        Items.Generator.Element == YapItem<Value, Metadata>,
+        Items, Value, Metadata>(_ items: Items, queue: DispatchQueue = DispatchQueue.main, completion: (([YapItem<Value, Metadata>]) -> Void)? = .none) where
+        Items: Sequence,
+        Items.Iterator.Element == YapItem<Value, Metadata>,
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value,
+        Value.Coder.Value == Value,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(items: Items, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: ([YapItem<Value, Metadata>] -> Void)? = .None) {
+        Metadata.Coder.Value == Metadata {
             asyncWrite({ $0.writeWithMetadata(items) }, queue: queue, completion: completion)
     }
 }
diff --git a/Sources/Functional_ValueWithNoMetadata.swift b/Sources/Functional_ValueWithNoMetadata.swift
index a29a136..156a4b9 100644
--- a/Sources/Functional_ValueWithNoMetadata.swift
+++ b/Sources/Functional_ValueWithNoMetadata.swift
@@ -21,12 +21,12 @@ extension ReadTransactionType {
     - returns: an optional `ItemType`
     */
     public func readAtIndex<
-        Value where
+        Value>(_ index: YapDB.Index) -> Value? where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value>(index: YapDB.Index) -> Value? {
-            return Value.decode(readAtIndex(index))
+        Value.Coder.Value == Value {
+            return Value.decode(readAtIndex(index) as Any?)
     }
 
     /**
@@ -36,14 +36,14 @@ extension ReadTransactionType {
     - returns: an array of `ItemType`
     */
     public func readAtIndexes<
-        Indexes, Value where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, Value>(_ indexes: Indexes) -> [Value?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value>(indexes: Indexes) -> [Value] {
-            return indexes.flatMap(readAtIndex)
+        Value.Coder.Value == Value {
+            return indexes.map(readAtIndex)
     }
 
     /**
@@ -53,11 +53,11 @@ extension ReadTransactionType {
     - returns: an optional `ItemType`
     */
     public func readByKey<
-        Value where
+        Value>(_ key: String) -> Value? where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value>(key: String) -> Value? {
+        Value.Coder.Value == Value {
             return readAtIndex(Value.indexWithKey(key))
     }
 
@@ -68,13 +68,13 @@ extension ReadTransactionType {
     - returns: an array of `ItemType`
     */
     public func readByKeys<
-        Keys, Value where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
+        Keys, Value>(_ keys: Keys) -> [Value?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value>(keys: Keys) -> [Value] {
+        Value.Coder.Value == Value {
             return readAtIndexes(Value.indexesWithKeys(keys))
     }
 
@@ -84,11 +84,11 @@ extension ReadTransactionType {
     - returns: an array of `ItemType`
     */
     public func readAll<
-        Value where
+        Value>() -> [Value?] where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value>() -> [Value] {
+        Value.Coder.Value == Value {
             return readByKeys(keysInCollection(Value.collection))
     }
 }
@@ -102,11 +102,11 @@ extension ConnectionType {
     - returns: an optional `ItemType`
     */
     public func readAtIndex<
-        Value where
+        Value>(_ index: YapDB.Index) -> Value? where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value>(index: YapDB.Index) -> Value? {
+        Value.Coder.Value == Value {
             return read { $0.readAtIndex(index) }
     }
 
@@ -117,13 +117,13 @@ extension ConnectionType {
     - returns: an array of `ItemType`
     */
     public func readAtIndexes<
-        Indexes, Value where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, Value>(_ indexes: Indexes) -> [Value?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value>(indexes: Indexes) -> [Value] {
+        Value.Coder.Value == Value {
             return read { $0.readAtIndexes(indexes) }
     }
 
@@ -134,11 +134,11 @@ extension ConnectionType {
     - returns: an optional `ItemType`
     */
     public func readByKey<
-        Value where
+        Value>(_ key: String) -> Value? where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value>(key: String) -> Value? {
+        Value.Coder.Value == Value {
             return readAtIndex(Value.indexWithKey(key))
     }
 
@@ -149,13 +149,13 @@ extension ConnectionType {
     - returns: an array of `ItemType`
     */
     public func readByKeys<
-        Keys, Value where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
+        Keys, Value>(_ keys: Keys) -> [Value?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value>(keys: Keys) -> [Value] {
+        Value.Coder.Value == Value {
             return readAtIndexes(Value.indexesWithKeys(keys))
     }
 
@@ -165,11 +165,11 @@ extension ConnectionType {
     - returns: an array of `ItemType`
     */
     public func readAll<
-        Value where
+        Value>() -> [Value?] where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value>() -> [Value] {
+        Value.Coder.Value == Value {
             return read { $0.readAll() }
     }
 }
@@ -184,12 +184,12 @@ extension WriteTransactionType {
     - parameter item: the item to store.
     */
     public func write<
-        Value where
+        Value>(_ item: Value) -> Value where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value>(item: Value) -> Value {
-            writeAtIndex(item.index, object: item.encoded, metadata: .None)
+        Value.Coder.Value == Value {
+            writeAtIndex(item.index, object: item.encoded, metadata: .none)
             return item
     }
 
@@ -199,13 +199,13 @@ extension WriteTransactionType {
     - parameter items: a SequenceType of items to store.
     */
     public func write<
-        Items, Value where
-        Items: SequenceType,
-        Items.Generator.Element == Value,
+        Items, Value>(_ items: Items) -> [Value] where
+        Items: Sequence,
+        Items.Iterator.Element == Value,
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value>(items: Items) -> [Value] {
+        Value.Coder.Value == Value {
             return items.map(write)
     }
 }
@@ -218,11 +218,11 @@ extension ConnectionType {
     - parameter item: the item to store.
     */
     public func write<
-        Value where
+        Value>(_ item: Value) -> Value where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value>(item: Value) -> Value {
+        Value.Coder.Value == Value {
             return write { $0.write(item) }
     }
 
@@ -232,13 +232,13 @@ extension ConnectionType {
     - parameter items: a SequenceType of items to store.
     */
     public func write<
-        Items, Value where
-        Items: SequenceType,
-        Items.Generator.Element == Value,
+        Items, Value>(_ items: Items) -> [Value] where
+        Items: Sequence,
+        Items.Iterator.Element == Value,
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value>(items: Items) -> [Value] {
+        Value.Coder.Value == Value {
             return write { $0.write(items) }
     }
 
@@ -250,11 +250,11 @@ extension ConnectionType {
     - parameter completion: a dispatch_block_t for completion.
     */
     public func asyncWrite<
-        Value where
+        Value>(_ item: Value, queue: DispatchQueue = DispatchQueue.main, completion: ((Value) -> Void)? = .none) where
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value>(item: Value, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: (Value -> Void)? = .None) {
+        Value.Coder.Value == Value {
             asyncWrite({ $0.write(item) }, queue: queue, completion: completion)
     }
 
@@ -266,13 +266,13 @@ extension ConnectionType {
     - parameter completion: a dispatch_block_t for completion.
     */
     public func asyncWrite<
-        Items, Value where
-        Items: SequenceType,
-        Items.Generator.Element == Value,
+        Items, Value>(_ items: Items, queue: DispatchQueue = DispatchQueue.main, completion: (([Value]) -> Void)? = .none) where
+        Items: Sequence,
+        Items.Iterator.Element == Value,
         Value: Persistable,
         Value: ValueCoding,
         Value.Coder: NSCoding,
-        Value.Coder.ValueType == Value>(items: Items, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: ([Value] -> Void)? = .None) {
+        Value.Coder.Value == Value {
             asyncWrite({ $0.write(items) }, queue: queue, completion: completion)
     }
 }
diff --git a/Sources/Persistable_AnyWithObjectMetadata.swift b/Sources/Persistable_AnyWithObjectMetadata.swift
index fbe08ed..ed3e226 100644
--- a/Sources/Persistable_AnyWithObjectMetadata.swift
+++ b/Sources/Persistable_AnyWithObjectMetadata.swift
@@ -14,24 +14,24 @@ import ValueCoding
 extension Readable where
     ItemType: Persistable {
 
-    func metadataInTransaction<Metadata: NSCoding>(transaction: Database.Connection.ReadTransaction, atIndex index: YapDB.Index) -> Metadata? {
+    func metadataInTransaction<Metadata: NSCoding>(_ transaction: Database.Connection.ReadTransaction, atIndex index: YapDB.Index) -> Metadata? {
         return transaction.readMetadataAtIndex(index)
     }
 
-    func metadataAtIndexInTransaction<Metadata: NSCoding>(index: YapDB.Index) -> Database.Connection.ReadTransaction -> Metadata? {
+    func metadataAtIndexInTransaction<Metadata: NSCoding>(_ index: YapDB.Index) -> (Database.Connection.ReadTransaction) -> Metadata? {
         return { self.metadataInTransaction($0, atIndex: index) }
     }
 
-    func metadataInTransactionAtIndex<Metadata: NSCoding>(transaction: Database.Connection.ReadTransaction) -> YapDB.Index -> Metadata? {
+    func metadataInTransactionAtIndex<Metadata: NSCoding>(_ transaction: Database.Connection.ReadTransaction) -> (YapDB.Index) -> Metadata? {
         return { self.metadataInTransaction(transaction, atIndex: $0) }
     }
 
     func metadataAtIndexesInTransaction<
-        Indexes, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
-        Metadata: NSCoding>(indexes: Indexes) -> Database.Connection.ReadTransaction -> [Metadata] {
-            return { indexes.flatMap(self.metadataInTransactionAtIndex($0)) }
+        Indexes, Metadata>(_ indexes: Indexes) -> (Database.Connection.ReadTransaction) -> [Metadata?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
+        Metadata: NSCoding {
+            return { indexes.map(self.metadataInTransactionAtIndex($0)) }
     }
 
     /**
@@ -41,8 +41,8 @@ extension Readable where
     - returns: an optional `Metadata`
     */
     public func metadataAtIndex<
-        Metadata where
-        Metadata: NSCoding>(index: YapDB.Index) -> Metadata? {
+        Metadata>(_ index: YapDB.Index) -> Metadata? where
+        Metadata: NSCoding {
         return sync(metadataAtIndexInTransaction(index))
     }
 
@@ -53,10 +53,10 @@ extension Readable where
     - returns: an array of `Metadata`
     */
     public func metadataAtIndexes<
-        Indexes, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
-        Metadata: NSCoding>(indexes: Indexes) -> [Metadata] {
+        Indexes, Metadata>(_ indexes: Indexes) -> [Metadata?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
+        Metadata: NSCoding {
             return sync(metadataAtIndexesInTransaction(indexes))
     }
 }
diff --git a/Sources/Persistable_AnyWithValueMetadata.swift b/Sources/Persistable_AnyWithValueMetadata.swift
index 9147903..ceeb1a1 100644
--- a/Sources/Persistable_AnyWithValueMetadata.swift
+++ b/Sources/Persistable_AnyWithValueMetadata.swift
@@ -15,37 +15,37 @@ extension Readable where
     ItemType: Persistable {
 
     func metadataInTransaction<
-        Metadata where
+        Metadata>(_ transaction: Database.Connection.ReadTransaction, atIndex index: YapDB.Index) -> Metadata? where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(transaction: Database.Connection.ReadTransaction, atIndex index: YapDB.Index) -> Metadata? {
+        Metadata.Coder.Value == Metadata {
         return transaction.readMetadataAtIndex(index)
     }
 
     func metadataAtIndexInTransaction<
-        Metadata where
+        Metadata>(_ index: YapDB.Index) -> (Database.Connection.ReadTransaction) -> Metadata? where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(index: YapDB.Index) -> Database.Connection.ReadTransaction -> Metadata? {
+        Metadata.Coder.Value == Metadata {
         return { self.metadataInTransaction($0, atIndex: index) }
     }
 
     func metadataInTransactionAtIndex<
-        Metadata where
+        Metadata>(_ transaction: Database.Connection.ReadTransaction) -> (YapDB.Index) -> Metadata? where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(transaction: Database.Connection.ReadTransaction) -> YapDB.Index -> Metadata? {
+        Metadata.Coder.Value == Metadata {
         return { self.metadataInTransaction(transaction, atIndex: $0) }
     }
 
     func metadataAtIndexesInTransaction<
-        Indexes, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, Metadata>(_ indexes: Indexes) -> (Database.Connection.ReadTransaction) -> [Metadata?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(indexes: Indexes) -> Database.Connection.ReadTransaction -> [Metadata] {
-            return { indexes.flatMap(self.metadataInTransactionAtIndex($0)) }
+        Metadata.Coder.Value == Metadata {
+            return { indexes.map(self.metadataInTransactionAtIndex($0)) }
     }
 
     /**
@@ -55,10 +55,10 @@ extension Readable where
     - returns: an optional `Metadata`
     */
     public func metadataAtIndex<
-        Metadata where
+        Metadata>(_ index: YapDB.Index) -> Metadata? where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(index: YapDB.Index) -> Metadata? {
+        Metadata.Coder.Value == Metadata {
         return sync(metadataAtIndexInTransaction(index))
     }
 
@@ -69,12 +69,12 @@ extension Readable where
     - returns: an array of `Metadata`
     */
     public func metadataAtIndexes<
-        Indexes, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, Metadata>(_ indexes: Indexes) -> [Metadata?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(indexes: Indexes) -> [Metadata] {
+        Metadata.Coder.Value == Metadata {
             return sync(metadataAtIndexesInTransaction(indexes))
     }
 }
diff --git a/Sources/Persistable_ObjectWithNoMetadata.swift b/Sources/Persistable_ObjectWithNoMetadata.swift
index e390fd0..52072d6 100644
--- a/Sources/Persistable_ObjectWithNoMetadata.swift
+++ b/Sources/Persistable_ObjectWithNoMetadata.swift
@@ -22,7 +22,7 @@ extension Persistable where
     - parameter transaction: a YapDatabaseReadWriteTransaction
     - returns: the receiver.
     */
-    public func write<WriteTransaction: WriteTransactionType>(transaction: WriteTransaction) -> Self {
+    public func write<WriteTransaction: WriteTransactionType>(_ transaction: WriteTransaction) -> Self {
         return transaction.write(self)
     }
 
@@ -32,7 +32,7 @@ extension Persistable where
     - parameter connection: a YapDatabaseConnection
     - returns: the receiver.
     */
-    public func write<Connection: ConnectionType>(connection: Connection) -> Self {
+    public func write<Connection: ConnectionType>(_ connection: Connection) -> Self {
         return connection.write(self)
     }
 
@@ -42,7 +42,7 @@ extension Persistable where
     - parameter connection: a YapDatabaseConnection
     - returns: a closure which receives as an argument the receiver of this function.
     */
-    public func asyncWrite<Connection: ConnectionType>(connection: Connection, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: (Self -> Void)? = .None) {
+    public func asyncWrite<Connection: ConnectionType>(_ connection: Connection, queue: DispatchQueue = DispatchQueue.main, completion: ((Self) -> Void)? = .none) {
         return connection.asyncWrite(self, queue: queue, completion: completion)
     }
 
@@ -52,14 +52,14 @@ extension Persistable where
     - parameter connection: a YapDatabaseConnection
     - returns: an `NSOperation`
     */
-    public func writeOperation<Connection: ConnectionType>(connection: Connection) -> NSOperation {
-        return NSBlockOperation { connection.write(self) }
+    public func writeOperation<Connection: ConnectionType>(_ connection: Connection) -> Operation {
+        return BlockOperation { _ = connection.write(self) }
     }
 }
 
-extension SequenceType where
-    Generator.Element: Persistable,
-    Generator.Element: NSCoding {
+extension Sequence where
+    Iterator.Element: Persistable,
+    Iterator.Element: NSCoding {
 
     /**
     Write the items using an existing transaction.
@@ -67,7 +67,7 @@ extension SequenceType where
     - parameter transaction: a WriteTransactionType e.g. YapDatabaseReadWriteTransaction
     - returns: the receiver.
     */
-    public func write<WriteTransaction: WriteTransactionType>(transaction: WriteTransaction) -> [Generator.Element] {
+    public func write<WriteTransaction: WriteTransactionType>(_ transaction: WriteTransaction) -> [Iterator.Element] {
         return transaction.write(self)
     }
 
@@ -77,7 +77,7 @@ extension SequenceType where
     - parameter connection: a ConnectionType e.g. YapDatabaseConnection
     - returns: the receiver.
     */
-    public func write<Connection: ConnectionType>(connection: Connection) -> [Generator.Element] {
+    public func write<Connection: ConnectionType>(_ connection: Connection) -> [Iterator.Element] {
         return connection.write(self)
     }
 
@@ -87,7 +87,7 @@ extension SequenceType where
     - parameter connection: a ConnectionType e.g. YapDatabaseConnection
     - returns: a closure which receives as an argument the receiver of this function.
     */
-    public func asyncWrite<Connection: ConnectionType>(connection: Connection, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: ([Generator.Element] -> Void)? = .None) {
+    public func asyncWrite<Connection: ConnectionType>(_ connection: Connection, queue: DispatchQueue = DispatchQueue.main, completion: (([Iterator.Element]) -> Void)? = .none) {
         return connection.asyncWrite(self, queue: queue, completion: completion)
     }
 
@@ -97,8 +97,8 @@ extension SequenceType where
     - parameter connection: a YapDatabaseConnection
     - returns: an `NSOperation`
     */
-    public func writeOperation<Connection: ConnectionType>(connection: Connection) -> NSOperation {
-        return NSBlockOperation { connection.write(self) }
+    public func writeOperation<Connection: ConnectionType>(_ connection: Connection) -> Operation {
+        return BlockOperation { _ = connection.write(self) }
     }
 }
 
@@ -108,43 +108,43 @@ extension Readable where
     ItemType: NSCoding,
     ItemType: Persistable {
 
-    func inTransaction(transaction: Database.Connection.ReadTransaction, atIndex index: YapDB.Index) -> ItemType? {
+    func inTransaction(_ transaction: Database.Connection.ReadTransaction, atIndex index: YapDB.Index) -> ItemType? {
         return transaction.readAtIndex(index)
     }
 
-    func inTransactionAtIndex(transaction: Database.Connection.ReadTransaction) -> YapDB.Index -> ItemType? {
+    func inTransactionAtIndex(_ transaction: Database.Connection.ReadTransaction) -> (YapDB.Index) -> ItemType? {
         return { self.inTransaction(transaction, atIndex: $0) }
     }
 
-    func atIndexInTransaction(index: YapDB.Index) -> Database.Connection.ReadTransaction -> ItemType? {
+    func atIndexInTransaction(_ index: YapDB.Index) -> (Database.Connection.ReadTransaction) -> ItemType? {
         return { self.inTransaction($0, atIndex: index) }
     }
 
     func atIndexesInTransaction<
-        Indexes where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index>(indexes: Indexes) -> Database.Connection.ReadTransaction -> [ItemType] {
+        Indexes>(_ indexes: Indexes) -> (Database.Connection.ReadTransaction) -> [ItemType?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index {
             let atIndex = inTransactionAtIndex
-            return { indexes.flatMap(atIndex($0)) }
+            return { indexes.map(atIndex($0)) }
     }
 
-    func inTransaction(transaction: Database.Connection.ReadTransaction, byKey key: String) -> ItemType? {
+    func inTransaction(_ transaction: Database.Connection.ReadTransaction, byKey key: String) -> ItemType? {
         return inTransaction(transaction, atIndex: ItemType.indexWithKey(key))
     }
 
-    func inTransactionByKey(transaction: Database.Connection.ReadTransaction) -> String -> ItemType? {
+    func inTransactionByKey(_ transaction: Database.Connection.ReadTransaction) -> (String) -> ItemType? {
         return { self.inTransaction(transaction, byKey: $0) }
     }
 
-    func byKeyInTransaction(key: String) -> Database.Connection.ReadTransaction -> ItemType? {
+    func byKeyInTransaction(_ key: String) -> (Database.Connection.ReadTransaction) -> ItemType? {
         return { self.inTransaction($0, byKey: key) }
     }
 
-    func byKeysInTransaction(keys: [String]? = .None) -> Database.Connection.ReadTransaction -> [ItemType] {
+    func byKeysInTransaction(_ keys: [String]? = .none) -> (Database.Connection.ReadTransaction) -> [ItemType?] {
         let byKey = inTransactionByKey
         return { transaction in
             let keys = keys ?? transaction.keysInCollection(ItemType.collection)
-            return keys.flatMap(byKey(transaction))
+            return keys.map(byKey(transaction))
         }
     }
 
@@ -154,7 +154,7 @@ extension Readable where
     - parameter index: a YapDB.Index
     - returns: an optional `ItemType`
     */
-    public func atIndex(index: YapDB.Index) -> ItemType? {
+    public func atIndex(_ index: YapDB.Index) -> ItemType? {
         return sync(atIndexInTransaction(index))
     }
 
@@ -165,9 +165,9 @@ extension Readable where
     - returns: an array of `ItemType`
     */
     public func atIndexes<
-        Indexes where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index>(indexes: Indexes) -> [ItemType] {
+        Indexes>(_ indexes: Indexes) -> [ItemType?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index {
             return sync(atIndexesInTransaction(indexes))
     }
 
@@ -177,7 +177,7 @@ extension Readable where
     - parameter key: a String
     - returns: an optional `ItemType`
     */
-    public func byKey(key: String) -> ItemType? {
+    public func byKey(_ key: String) -> ItemType? {
         return sync(byKeyInTransaction(key))
     }
 
@@ -188,9 +188,9 @@ extension Readable where
     - returns: an array of `ItemType`
     */
     public func byKeys<
-        Keys where
-        Keys: SequenceType,
-        Keys.Generator.Element == String>(keys: Keys) -> [ItemType] {
+        Keys>(_ keys: Keys) -> [ItemType?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String {
             return sync(byKeysInTransaction(Array(keys)))
     }
 
@@ -199,7 +199,7 @@ extension Readable where
 
     - returns: an array of `ItemType`
     */
-    public func all() -> [ItemType] {
+    public func all() -> [ItemType?] {
         return sync(byKeysInTransaction())
     }
 
@@ -209,12 +209,18 @@ extension Readable where
     - parameter keys: a SequenceType of String values
     - returns: a tuple of type `([ItemType], [String])`
     */
-    public func filterExisting(keys: [String]) -> (existing: [ItemType], missing: [String]) {
+    public func filterExisting(_ keys: [String]) -> (existing: [ItemType], missing: [String]) {
         let existingInTransaction = byKeysInTransaction(keys)
         return sync { transaction -> ([ItemType], [String]) in
-            let existing = existingInTransaction(transaction)
-            let existingKeys = existing.map(keyForPersistable)
-            let missingKeys = keys.filter { !existingKeys.contains($0) }
+            var missingKeys = [String]()
+            let maybeExisting = existingInTransaction(transaction)
+            let existing = zip(keys, maybeExisting).flatMap { zipped -> ItemType? in
+                guard let item = zipped.1 else {
+                    missingKeys.append(zipped.0)
+                    return nil
+                }
+                return item
+            }
             return (existing, missingKeys)
         }
     }
diff --git a/Sources/Persistable_ObjectWithObjectMetadata.swift b/Sources/Persistable_ObjectWithObjectMetadata.swift
index abc3f22..4f33c88 100644
--- a/Sources/Persistable_ObjectWithObjectMetadata.swift
+++ b/Sources/Persistable_ObjectWithObjectMetadata.swift
@@ -22,9 +22,9 @@ extension Persistable where
     - returns: the receiver.
     */
     public func writeWithMetadata<
-        WriteTransaction, Metadata where
+        WriteTransaction, Metadata>(_ transaction: WriteTransaction, metadata: Metadata?) -> YapItem<Self, Metadata> where
         WriteTransaction: WriteTransactionType,
-        Metadata: NSCoding>(transaction: WriteTransaction, metadata: Metadata?) -> YapItem<Self, Metadata> {
+        Metadata: NSCoding {
         return transaction.writeWithMetadata(YapItem(self, metadata))
     }
 
@@ -35,9 +35,9 @@ extension Persistable where
     - returns: the receiver.
     */
     public func writeWithMetadata<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: Metadata?) -> YapItem<Self, Metadata> where
         Connection: ConnectionType,
-        Metadata: NSCoding>(connection: Connection, metadata: Metadata?) -> YapItem<Self, Metadata> {
+        Metadata: NSCoding {
         return connection.writeWithMetadata(YapItem(self, metadata))
     }
 
@@ -48,9 +48,9 @@ extension Persistable where
     - returns: a closure which receives as an argument the receiver of this function.
     */
     public func asyncWriteWithMetadata<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: Metadata?, queue: DispatchQueue = DispatchQueue.main, completion: ((YapItem<Self, Metadata>) -> Void)? = .none) where
         Connection: ConnectionType,
-        Metadata: NSCoding>(connection: Connection, metadata: Metadata?, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: (YapItem<Self, Metadata> -> Void)? = .None) {
+        Metadata: NSCoding {
         return connection.asyncWriteWithMetadata(YapItem(self, metadata), queue: queue, completion: completion)
     }
 
@@ -61,16 +61,16 @@ extension Persistable where
     - returns: an `NSOperation`
     */
     public func writeWithMetadataOperation<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: Metadata?) -> Operation where
         Connection: ConnectionType,
-        Metadata: NSCoding>(connection: Connection, metadata: Metadata?) -> NSOperation {
-        return NSBlockOperation { connection.writeWithMetadata(YapItem(self, metadata)) }
+        Metadata: NSCoding {
+        return BlockOperation { _ = connection.writeWithMetadata(YapItem(self, metadata)) }
     }
 }
 
-extension SequenceType where
-    Generator.Element: Persistable,
-    Generator.Element: NSCoding {
+extension Sequence where
+    Iterator.Element: Persistable,
+    Iterator.Element: NSCoding {
 
     /**
      Zips the receiver with metadata into an array of YapItem.
@@ -80,10 +80,10 @@ extension SequenceType where
      - returns: an array where Persistables and Metadata with corresponding indexes in `self` and `metadata` are joined in a `YapItem`
      */
     public func yapItems<
-        Metadatas, Metadata where
+        Metadatas, Metadata>(with metadata: Metadatas) -> [YapItem<Iterator.Element, Metadata>] where
         Metadata: NSCoding,
-        Metadatas: SequenceType,
-        Metadatas.Generator.Element == Optional<Metadata>>(with metadata: Metadatas) -> [YapItem<Generator.Element, Metadata>] {
+        Metadatas: Sequence,
+        Metadatas.Iterator.Element == Optional<Metadata> {
         return zip(self, metadata).map { YapItem($0, $1) }
     }
 
@@ -94,9 +94,9 @@ extension SequenceType where
     - returns: the receiver.
     */
     public func writeWithMetadata<
-        WriteTransaction, Metadata where
+        WriteTransaction, Metadata>(_ transaction: WriteTransaction, metadata: [Metadata?]) -> [YapItem<Iterator.Element, Metadata>] where
         WriteTransaction: WriteTransactionType,
-        Metadata: NSCoding>(transaction: WriteTransaction, metadata: [Metadata?]) -> [YapItem<Generator.Element, Metadata>] {
+        Metadata: NSCoding {
         let items = yapItems(with: metadata)
         return transaction.writeWithMetadata(items)
     }
@@ -108,9 +108,9 @@ extension SequenceType where
     - returns: the receiver.
     */
     public func writeWithMetadata<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: [Metadata?]) -> [YapItem<Iterator.Element, Metadata>] where
         Connection: ConnectionType,
-        Metadata: NSCoding>(connection: Connection, metadata: [Metadata?]) -> [YapItem<Generator.Element, Metadata>] {
+        Metadata: NSCoding {
         let items = yapItems(with: metadata)
         return connection.writeWithMetadata(items)
     }
@@ -122,9 +122,9 @@ extension SequenceType where
     - returns: a closure which receives as an argument the receiver of this function.
     */
     public func asyncWriteWithMetadata<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: [Metadata?], queue: DispatchQueue = DispatchQueue.main, completion: (([YapItem<Iterator.Element, Metadata>]) -> Void)? = .none) where
         Connection: ConnectionType,
-        Metadata: NSCoding>(connection: Connection, metadata: [Metadata?], queue: dispatch_queue_t = dispatch_get_main_queue(), completion: ([YapItem<Generator.Element, Metadata>] -> Void)? = .None) {
+        Metadata: NSCoding {
         let items = yapItems(with: metadata)
         return connection.asyncWriteWithMetadata(items, queue: queue, completion: completion)
     }
@@ -136,11 +136,11 @@ extension SequenceType where
     - returns: an `NSOperation`
     */
     public func writeWithMetadataOperation<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: [Metadata?]) -> Operation where
         Connection: ConnectionType,
-        Metadata: NSCoding>(connection: Connection, metadata: [Metadata?]) -> NSOperation {
+        Metadata: NSCoding {
         let items = yapItems(with: metadata)
-        return NSBlockOperation { connection.writeWithMetadata(items) }
+        return BlockOperation { _ = connection.writeWithMetadata(items) }
     }
 }
 
@@ -151,42 +151,42 @@ extension Readable where
     ItemType: NSCoding,
     ItemType: Persistable {
 
-    func withMetadataInTransaction<Metadata: NSCoding>(transaction: Database.Connection.ReadTransaction, atIndex index: YapDB.Index) -> YapItem<ItemType, Metadata>? {
+    func withMetadataInTransaction<Metadata: NSCoding>(_ transaction: Database.Connection.ReadTransaction, atIndex index: YapDB.Index) -> YapItem<ItemType, Metadata>? {
         return transaction.readWithMetadataAtIndex(index)
     }
 
-    func withMetadataInTransactionAtIndex<Metadata: NSCoding>(transaction: Database.Connection.ReadTransaction) -> YapDB.Index -> YapItem<ItemType, Metadata>? {
+    func withMetadataInTransactionAtIndex<Metadata: NSCoding>(_ transaction: Database.Connection.ReadTransaction) -> (YapDB.Index) -> YapItem<ItemType, Metadata>? {
         return { self.withMetadataInTransaction(transaction, atIndex: $0) }
     }
 
-    func withMetadataAtIndexInTransaction<Metadata: NSCoding>(index: YapDB.Index) -> Database.Connection.ReadTransaction -> YapItem<ItemType, Metadata>? {
+    func withMetadataAtIndexInTransaction<Metadata: NSCoding>(_ index: YapDB.Index) -> (Database.Connection.ReadTransaction) -> YapItem<ItemType, Metadata>? {
         return { self.withMetadataInTransaction($0, atIndex: index) }
     }
 
     func withMetadataAtIndexesInTransaction<
-        Indexes, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
-        Metadata: NSCoding>(indexes: Indexes) -> Database.Connection.ReadTransaction -> [YapItem<ItemType, Metadata>] {
-            return { indexes.flatMap(self.withMetadataInTransactionAtIndex($0)) }
+        Indexes, Metadata>(_ indexes: Indexes) -> (Database.Connection.ReadTransaction) -> [YapItem<ItemType, Metadata>?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
+        Metadata: NSCoding {
+            return { indexes.map(self.withMetadataInTransactionAtIndex($0)) }
     }
 
-    func withMetadataInTransaction<Metadata: NSCoding>(transaction: Database.Connection.ReadTransaction, byKey key: String) -> YapItem<ItemType, Metadata>? {
+    func withMetadataInTransaction<Metadata: NSCoding>(_ transaction: Database.Connection.ReadTransaction, byKey key: String) -> YapItem<ItemType, Metadata>? {
         return withMetadataInTransaction(transaction, atIndex: ItemType.indexWithKey(key))
     }
 
-    func withMetadataInTransactionByKey<Metadata: NSCoding>(transaction: Database.Connection.ReadTransaction) -> String -> YapItem<ItemType, Metadata>? {
+    func withMetadataInTransactionByKey<Metadata: NSCoding>(_ transaction: Database.Connection.ReadTransaction) -> (String) -> YapItem<ItemType, Metadata>? {
         return { self.withMetadataInTransaction(transaction, byKey: $0) }
     }
 
-    func withMetadataByKeyInTransaction<Metadata: NSCoding>(key: String) -> Database.Connection.ReadTransaction -> YapItem<ItemType, Metadata>? {
+    func withMetadataByKeyInTransaction<Metadata: NSCoding>(_ key: String) -> (Database.Connection.ReadTransaction) -> YapItem<ItemType, Metadata>? {
         return { self.withMetadataInTransaction($0, byKey: key) }
     }
 
-    func withMetadataByKeysInTransaction<Metadata: NSCoding>(keys: [String]? = .None) -> Database.Connection.ReadTransaction -> [YapItem<ItemType, Metadata>] {
+    func withMetadataByKeysInTransaction<Metadata: NSCoding>(_ keys: [String]? = .none) -> (Database.Connection.ReadTransaction) -> [YapItem<ItemType, Metadata>?] {
         return { transaction in
             let keys = keys ?? transaction.keysInCollection(ItemType.collection)
-            return keys.flatMap(self.withMetadataInTransactionByKey(transaction))
+            return keys.map(self.withMetadataInTransactionByKey(transaction))
         }
     }
 
@@ -196,7 +196,7 @@ extension Readable where
     - parameter index: a YapDB.Index
     - returns: an optional `ItemType`
     */
-    public func withMetadataAtIndex<Metadata: NSCoding>(index: YapDB.Index) -> YapItem<ItemType, Metadata>? {
+    public func withMetadataAtIndex<Metadata: NSCoding>(_ index: YapDB.Index) -> YapItem<ItemType, Metadata>? {
         return sync(withMetadataAtIndexInTransaction(index))
     }
 
@@ -207,10 +207,10 @@ extension Readable where
     - returns: an array of `ItemType`
     */
     public func withMetadataAtIndexes<
-        Indexes, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
-        Metadata: NSCoding>(indexes: Indexes) -> [YapItem<ItemType, Metadata>] {
+        Indexes, Metadata>(_ indexes: Indexes) -> [YapItem<ItemType, Metadata>?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
+        Metadata: NSCoding {
             return sync(withMetadataAtIndexesInTransaction(indexes))
     }
 
@@ -220,7 +220,7 @@ extension Readable where
     - parameter key: a String
     - returns: an optional `ItemType`
     */
-    public func withMetadataByKey<Metadata: NSCoding>(key: String) -> YapItem<ItemType, Metadata>? {
+    public func withMetadataByKey<Metadata: NSCoding>(_ key: String) -> YapItem<ItemType, Metadata>? {
         return sync(withMetadataByKeyInTransaction(key))
     }
 
@@ -231,10 +231,10 @@ extension Readable where
     - returns: an array of `ItemType`
     */
     public func withMetadataByKeys<
-        Keys, Metadata where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
-        Metadata: NSCoding>(keys: Keys) -> [YapItem<ItemType, Metadata>] {
+        Keys, Metadata>(_ keys: Keys) -> [YapItem<ItemType, Metadata>?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
+        Metadata: NSCoding {
             return sync(withMetadataByKeysInTransaction(Array(keys)))
     }
 
@@ -243,7 +243,7 @@ extension Readable where
 
     - returns: an array of `ItemType`
     */
-    public func withMetadataAll<Metadata: NSCoding>() -> [YapItem<ItemType, Metadata>] {
+    public func withMetadataAll<Metadata: NSCoding>() -> [YapItem<ItemType, Metadata>?] {
         return sync(withMetadataByKeysInTransaction())
     }
 
@@ -253,12 +253,18 @@ extension Readable where
     - parameter keys: a SequenceType of String values
     - returns: a tuple of type `([ItemType], [String])`
     */
-    public func withMetadataFilterExisting<Metadata: NSCoding>(keys: [String]) -> (existing: [YapItem<ItemType, Metadata>], missing: [String]) {
-        let existingInTransaction: Database.Connection.ReadTransaction -> [YapItem<ItemType, Metadata>] = withMetadataByKeysInTransaction(keys)
+    public func withMetadataFilterExisting<Metadata: NSCoding>(_ keys: [String]) -> (existing: [YapItem<ItemType, Metadata>], missing: [String]) {
+        let existingInTransaction: (Database.Connection.ReadTransaction) -> [YapItem<ItemType, Metadata>?] = withMetadataByKeysInTransaction(keys)
         return sync { transaction -> ([YapItem<ItemType, Metadata>], [String]) in
-            let existing = existingInTransaction(transaction)
-            let existingKeys = existing.map {keyForPersistable($0.value)}
-            let missingKeys = keys.filter { !existingKeys.contains($0) }
+            var missingKeys = [String]()
+            let maybeExisting = existingInTransaction(transaction)
+            let existing = zip(keys, maybeExisting).flatMap { zipped -> YapItem<ItemType, Metadata>? in
+                guard let item = zipped.1 else {
+                    missingKeys.append(zipped.0)
+                    return nil
+                }
+                return item
+            }
             return (existing, missingKeys)
         }
     }
diff --git a/Sources/Persistable_ObjectWithValueMetadata.swift b/Sources/Persistable_ObjectWithValueMetadata.swift
index 3ca949f..e71fa2e 100644
--- a/Sources/Persistable_ObjectWithValueMetadata.swift
+++ b/Sources/Persistable_ObjectWithValueMetadata.swift
@@ -23,11 +23,11 @@ extension Persistable where
     - returns: the receiver.
     */
     public func writeWithMetadata<
-        WriteTransaction, Metadata where
+        WriteTransaction, Metadata>(_ transaction: WriteTransaction, metadata: Metadata?) -> YapItem<Self, Metadata> where
         WriteTransaction: WriteTransactionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(transaction: WriteTransaction, metadata: Metadata?) -> YapItem<Self, Metadata> {
+        Metadata.Coder.Value == Metadata {
         return transaction.writeWithMetadata(YapItem(self, metadata))
     }
 
@@ -38,11 +38,11 @@ extension Persistable where
     - returns: the receiver.
     */
     public func writeWithMetadata<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: Metadata?) -> YapItem<Self, Metadata> where
         Connection: ConnectionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(connection: Connection, metadata: Metadata?) -> YapItem<Self, Metadata> {
+        Metadata.Coder.Value == Metadata {
         return connection.writeWithMetadata(YapItem(self, metadata))
     }
 
@@ -53,11 +53,11 @@ extension Persistable where
     - returns: a closure which receives as an argument the receiver of this function.
     */
     public func asyncWriteWithMetadata<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: Metadata?, queue: DispatchQueue = DispatchQueue.main, completion: ((YapItem<Self, Metadata>) -> Void)? = .none) where
         Connection: ConnectionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(connection: Connection, metadata: Metadata?, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: (YapItem<Self, Metadata> -> Void)? = .None) {
+        Metadata.Coder.Value == Metadata {
         return connection.asyncWriteWithMetadata(YapItem(self, metadata), queue: queue, completion: completion)
     }
 
@@ -68,18 +68,18 @@ extension Persistable where
     - returns: an `NSOperation`
     */
     public func writeWithMetadataOperation<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: Metadata?) -> Operation where
         Connection: ConnectionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(connection: Connection, metadata: Metadata?) -> NSOperation {
-        return NSBlockOperation { connection.writeWithMetadata(YapItem(self, metadata)) }
+        Metadata.Coder.Value == Metadata {
+        return BlockOperation { _ = connection.writeWithMetadata(YapItem(self, metadata)) }
     }
 }
 
-extension SequenceType where
-    Generator.Element: Persistable,
-    Generator.Element: NSCoding {
+extension Sequence where
+    Iterator.Element: Persistable,
+    Iterator.Element: NSCoding {
 
     /**
      Zips the receiver with metadata into an array of YapItem.
@@ -89,12 +89,12 @@ extension SequenceType where
      - returns: an array where Persistables and Metadata with corresponding indexes in `self` and `metadata` are joined in a `YapItem`
      */
     public func yapItems<
-        Metadatas, Metadata where
+        Metadatas, Metadata>(with metadata: Metadatas) -> [YapItem<Iterator.Element, Metadata>] where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata,
-        Metadatas: SequenceType,
-        Metadatas.Generator.Element == Optional<Metadata>>(with metadata: Metadatas) -> [YapItem<Generator.Element, Metadata>] {
+        Metadata.Coder.Value == Metadata,
+        Metadatas: Sequence,
+        Metadatas.Iterator.Element == Optional<Metadata> {
         return zip(self, metadata).map { YapItem($0, $1) }
     }
 
@@ -105,11 +105,11 @@ extension SequenceType where
     - returns: the receiver.
     */
     public func writeWithMetadata<
-        WriteTransaction, Metadata where
+        WriteTransaction, Metadata>(_ transaction: WriteTransaction, metadata: [Metadata?]) -> [YapItem<Iterator.Element, Metadata>] where
         WriteTransaction: WriteTransactionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(transaction: WriteTransaction, metadata: [Metadata?]) -> [YapItem<Generator.Element, Metadata>] {
+        Metadata.Coder.Value == Metadata {
         let items = yapItems(with: metadata)
         return transaction.writeWithMetadata(items)
     }
@@ -121,11 +121,11 @@ extension SequenceType where
     - returns: the receiver.
     */
     public func writeWithMetadata<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: [Metadata?]) -> [YapItem<Iterator.Element, Metadata>] where
         Connection: ConnectionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(connection: Connection, metadata: [Metadata?]) -> [YapItem<Generator.Element, Metadata>] {
+        Metadata.Coder.Value == Metadata {
         let items = yapItems(with: metadata)
         return connection.writeWithMetadata(items)
     }
@@ -137,11 +137,11 @@ extension SequenceType where
     - returns: a closure which receives as an argument the receiver of this function.
     */
     public func asyncWriteWithMetadata<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: [Metadata?], queue: DispatchQueue = DispatchQueue.main, completion: (([YapItem<Iterator.Element, Metadata>]) -> Void)? = .none) where
         Connection: ConnectionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(connection: Connection, metadata: [Metadata?], queue: dispatch_queue_t = dispatch_get_main_queue(), completion: ([YapItem<Generator.Element, Metadata>] -> Void)? = .None) {
+        Metadata.Coder.Value == Metadata {
         let items = yapItems(with: metadata)
         return connection.asyncWriteWithMetadata(items, queue: queue, completion: completion)
     }
@@ -153,13 +153,13 @@ extension SequenceType where
     - returns: an `NSOperation`
     */
     public func writeWithMetadataOperation<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: [Metadata?]) -> Operation where
         Connection: ConnectionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(connection: Connection, metadata: [Metadata?]) -> NSOperation {
+        Metadata.Coder.Value == Metadata {
         let items = yapItems(with: metadata)
-        return NSBlockOperation { connection.writeWithMetadata(items) }
+        return BlockOperation { _ = connection.writeWithMetadata(items) }
     }
 }
 
@@ -170,71 +170,71 @@ extension Readable where
     ItemType: Persistable {
 
     func withMetadataInTransaction<
-        Metadata where
+        Metadata>(_ transaction: Database.Connection.ReadTransaction, atIndex index: YapDB.Index) -> YapItem<ItemType, Metadata>? where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(transaction: Database.Connection.ReadTransaction, atIndex index: YapDB.Index) -> YapItem<ItemType, Metadata>? {
+        Metadata.Coder.Value == Metadata {
         return transaction.readWithMetadataAtIndex(index)
     }
 
     func withMetadataInTransactionAtIndex<
-        Metadata where
+        Metadata>(_ transaction: Database.Connection.ReadTransaction) -> (YapDB.Index) -> YapItem<ItemType, Metadata>? where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(transaction: Database.Connection.ReadTransaction) -> YapDB.Index -> YapItem<ItemType, Metadata>? {
+        Metadata.Coder.Value == Metadata {
         return { self.withMetadataInTransaction(transaction, atIndex: $0) }
     }
 
     func withMetadataAtIndexInTransaction<
-        Metadata where
+        Metadata>(_ index: YapDB.Index) -> (Database.Connection.ReadTransaction) -> YapItem<ItemType, Metadata>? where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(index: YapDB.Index) -> Database.Connection.ReadTransaction -> YapItem<ItemType, Metadata>? {
+        Metadata.Coder.Value == Metadata {
         return { self.withMetadataInTransaction($0, atIndex: index) }
     }
 
     func withMetadataAtIndexesInTransaction<
-        Indexes, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, Metadata>(_ indexes: Indexes) -> (Database.Connection.ReadTransaction) -> [YapItem<ItemType, Metadata>?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(indexes: Indexes) -> Database.Connection.ReadTransaction -> [YapItem<ItemType, Metadata>] {
-            return { indexes.flatMap(self.withMetadataInTransactionAtIndex($0)) }
+        Metadata.Coder.Value == Metadata {
+            return { indexes.map(self.withMetadataInTransactionAtIndex($0)) }
     }
 
     func withMetadataInTransaction<
-        Metadata where
+        Metadata>(_ transaction: Database.Connection.ReadTransaction, byKey key: String) -> YapItem<ItemType, Metadata>? where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(transaction: Database.Connection.ReadTransaction, byKey key: String) -> YapItem<ItemType, Metadata>? {
+        Metadata.Coder.Value == Metadata {
         return withMetadataInTransaction(transaction, atIndex: ItemType.indexWithKey(key))
     }
 
     func withMetadataInTransactionByKey<
-        Metadata where
+        Metadata>(_ transaction: Database.Connection.ReadTransaction) -> (String) -> YapItem<ItemType, Metadata>? where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(transaction: Database.Connection.ReadTransaction) -> String -> YapItem<ItemType, Metadata>? {
+        Metadata.Coder.Value == Metadata {
         return { self.withMetadataInTransaction(transaction, byKey: $0) }
     }
 
     func withMetadataByKeyInTransaction<
-        Metadata where
+        Metadata>(_ key: String) -> (Database.Connection.ReadTransaction) -> YapItem<ItemType, Metadata>? where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(key: String) -> Database.Connection.ReadTransaction -> YapItem<ItemType, Metadata>? {
+        Metadata.Coder.Value == Metadata {
         return { self.withMetadataInTransaction($0, byKey: key) }
     }
 
     func withMetadataByKeysInTransaction<
-        Metadata where
+        Metadata>(_ keys: [String]? = .none) -> (Database.Connection.ReadTransaction) -> [YapItem<ItemType, Metadata>?] where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(keys: [String]? = .None) -> Database.Connection.ReadTransaction -> [YapItem<ItemType, Metadata>] {
+        Metadata.Coder.Value == Metadata {
         return { transaction in
             let keys = keys ?? transaction.keysInCollection(ItemType.collection)
-            return keys.flatMap(self.withMetadataInTransactionByKey(transaction))
+            return keys.map(self.withMetadataInTransactionByKey(transaction))
         }
     }
 
@@ -245,10 +245,10 @@ extension Readable where
     - returns: an optional `ItemType`
     */
     public func withMetadataAtIndex<
-        Metadata where
+        Metadata>(_ index: YapDB.Index) -> YapItem<ItemType, Metadata>? where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(index: YapDB.Index) -> YapItem<ItemType, Metadata>? {
+        Metadata.Coder.Value == Metadata {
         return sync(withMetadataAtIndexInTransaction(index))
     }
 
@@ -259,12 +259,12 @@ extension Readable where
     - returns: an array of `ItemType`
     */
     public func withMetadataAtIndexes<
-        Indexes, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, Metadata>(_ indexes: Indexes) -> [YapItem<ItemType, Metadata>?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(indexes: Indexes) -> [YapItem<ItemType, Metadata>] {
+        Metadata.Coder.Value == Metadata {
             return sync(withMetadataAtIndexesInTransaction(indexes))
     }
 
@@ -275,10 +275,10 @@ extension Readable where
     - returns: an optional `ItemType`
     */
     public func withMetadataByKey<
-        Metadata where
+        Metadata>(_ key: String) -> YapItem<ItemType, Metadata>? where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(key: String) -> YapItem<ItemType, Metadata>? {
+        Metadata.Coder.Value == Metadata {
         return sync(withMetadataByKeyInTransaction(key))
     }
 
@@ -289,12 +289,12 @@ extension Readable where
     - returns: an array of `ItemType`
     */
     public func withMetadataByKeys<
-        Keys, Metadata where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
+        Keys, Metadata>(_ keys: Keys) -> [YapItem<ItemType, Metadata>?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(keys: Keys) -> [YapItem<ItemType, Metadata>] {
+        Metadata.Coder.Value == Metadata {
             return sync(withMetadataByKeysInTransaction(Array(keys)))
     }
 
@@ -304,10 +304,10 @@ extension Readable where
     - returns: an array of `ItemType`
     */
     public func withMetadataAll<
-        Metadata where
+        Metadata>() -> [YapItem<ItemType, Metadata>?] where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>() -> [YapItem<ItemType, Metadata>] {
+        Metadata.Coder.Value == Metadata {
         return sync(withMetadataByKeysInTransaction())
     }
 
@@ -318,15 +318,21 @@ extension Readable where
     - returns: a tuple of type `([ItemType], [String])`
     */
     public func withMetadataFilterExisting<
-        Metadata where
+        Metadata>(_ keys: [String]) -> (existing: [YapItem<ItemType, Metadata>], missing: [String]) where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(keys: [String]) -> (existing: [YapItem<ItemType, Metadata>], missing: [String]) {
-        let existingInTransaction: Database.Connection.ReadTransaction -> [YapItem<ItemType, Metadata>] = withMetadataByKeysInTransaction(keys)
+        Metadata.Coder.Value == Metadata {
+        let existingInTransaction: (Database.Connection.ReadTransaction) -> [YapItem<ItemType, Metadata>?] = withMetadataByKeysInTransaction(keys)
         return sync { transaction -> ([YapItem<ItemType, Metadata>], [String]) in
-            let existing = existingInTransaction(transaction)
-            let existingKeys = existing.map {keyForPersistable($0.value)}
-            let missingKeys = keys.filter { !existingKeys.contains($0) }
+            var missingKeys = [String]()
+            let maybeExisting = existingInTransaction(transaction)
+            let existing = zip(keys, maybeExisting).flatMap { zipped -> YapItem<ItemType, Metadata>? in
+                guard let item = zipped.1 else {
+                    missingKeys.append(zipped.0)
+                    return nil
+                }
+                return item
+            }
             return (existing, missingKeys)
         }
     }
diff --git a/Sources/Persistable_Remove.swift b/Sources/Persistable_Remove.swift
index c99913f..62b1ba9 100644
--- a/Sources/Persistable_Remove.swift
+++ b/Sources/Persistable_Remove.swift
@@ -12,7 +12,7 @@ extension Persistable {
 
     - parameter transaction: a `WriteTransactionType` transaction
     */
-    public func remove<WriteTransaction: WriteTransactionType>(transaction: WriteTransaction) {
+    public func remove<WriteTransaction: WriteTransactionType>(_ transaction: WriteTransaction) {
         transaction.remove(self)
     }
 
@@ -21,7 +21,7 @@ extension Persistable {
 
     - parameter connection: a `ConnectionType` connection
     */
-    public func remove<Connection: ConnectionType>(connection: Connection) {
+    public func remove<Connection: ConnectionType>(_ connection: Connection) {
         connection.remove(self)
     }
 
@@ -30,7 +30,7 @@ extension Persistable {
 
     - parameter connection: a `ConnectionType` connection
     */
-    public func asyncRemove<Connection: ConnectionType>(connection: Connection, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: dispatch_block_t? = .None) {
+    public func asyncRemove<Connection: ConnectionType>(_ connection: Connection, queue: DispatchQueue = DispatchQueue.main, completion: (()->())? = .none) {
         connection.asyncRemove(self, queue: queue, completion: completion)
     }
 
@@ -40,20 +40,20 @@ extension Persistable {
 
     - parameter connection: a `ConnectionType` connection
     */
-    public func removeOperation<Connection: ConnectionType>(connection: Connection) -> NSOperation {
-        return NSBlockOperation { connection.remove(self) }
+    public func removeOperation<Connection: ConnectionType>(_ connection: Connection) -> Operation {
+        return BlockOperation { connection.remove(self) }
     }
 }
 
-extension SequenceType where
-Generator.Element: Persistable {
+extension Sequence where
+Iterator.Element: Persistable {
 
     /**
     Removes the receiver using the write transaction.
 
     - parameter transaction: a `WriteTransactionType` transaction
     */
-    public func remove<WriteTransaction: WriteTransactionType>(transaction: WriteTransaction) {
+    public func remove<WriteTransaction: WriteTransactionType>(_ transaction: WriteTransaction) {
         transaction.remove(self)
     }
 
@@ -62,7 +62,7 @@ Generator.Element: Persistable {
 
     - parameter connection: a `ConnectionType` connection
     */
-    public func remove<Connection: ConnectionType>(connection: Connection) {
+    public func remove<Connection: ConnectionType>(_ connection: Connection) {
         connection.remove(self)
     }
 
@@ -71,7 +71,7 @@ Generator.Element: Persistable {
 
     - parameter connection: a `ConnectionType` connection
     */
-    public func asyncRemove<Connection: ConnectionType>(connection: Connection, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: dispatch_block_t? = .None) {
+    public func asyncRemove<Connection: ConnectionType>(_ connection: Connection, queue: DispatchQueue = DispatchQueue.main, completion: (()->())? = .none) {
         connection.asyncRemove(self, queue: queue, completion: completion)
     }
 
@@ -81,8 +81,8 @@ Generator.Element: Persistable {
 
     - parameter connection: a `ConnectionType` connection
     */
-    public func removeOperation<Connection: ConnectionType>(connection: Connection) -> NSOperation {
-        return NSBlockOperation { connection.remove(self) }
+    public func removeOperation<Connection: ConnectionType>(_ connection: Connection) -> Operation {
+        return BlockOperation { connection.remove(self) }
     }
 }
 
diff --git a/Sources/Persistable_ValueWithNoMetadata.swift b/Sources/Persistable_ValueWithNoMetadata.swift
index 3e19487..40f8225 100644
--- a/Sources/Persistable_ValueWithNoMetadata.swift
+++ b/Sources/Persistable_ValueWithNoMetadata.swift
@@ -14,7 +14,7 @@ import ValueCoding
 extension Persistable where
     Self: ValueCoding,
     Self.Coder: NSCoding,
-    Self.Coder.ValueType == Self {
+    Self.Coder.Value == Self {
 
     // Writing
 
@@ -24,7 +24,7 @@ extension Persistable where
     - parameter transaction: a YapDatabaseReadWriteTransaction
     - returns: the receiver.
     */
-    public func write<WriteTransaction: WriteTransactionType>(transaction: WriteTransaction) -> Self {
+    public func write<WriteTransaction: WriteTransactionType>(_ transaction: WriteTransaction) -> Self {
         return transaction.write(self)
     }
 
@@ -34,7 +34,7 @@ extension Persistable where
     - parameter connection: a YapDatabaseConnection
     - returns: the receiver.
     */
-    public func write<Connection: ConnectionType>(connection: Connection) -> Self {
+    public func write<Connection: ConnectionType>(_ connection: Connection) -> Self {
         return connection.write(self)
     }
 
@@ -44,7 +44,7 @@ extension Persistable where
     - parameter connection: a YapDatabaseConnection
     - returns: a closure which receives as an argument the receiver of this function.
     */
-    public func asyncWrite<Connection: ConnectionType>(connection: Connection, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: (Self -> Void)? = .None) {
+    public func asyncWrite<Connection: ConnectionType>(_ connection: Connection, queue: DispatchQueue = DispatchQueue.main, completion: ((Self) -> Void)? = .none) {
         return connection.asyncWrite(self, queue: queue, completion: completion)
     }
 
@@ -54,16 +54,16 @@ extension Persistable where
     - parameter connection: a YapDatabaseConnection
     - returns: an `NSOperation`
     */
-    public func writeOperation<Connection: ConnectionType>(connection: Connection) -> NSOperation {
-        return NSBlockOperation { connection.write(self) }
+    public func writeOperation<Connection: ConnectionType>(_ connection: Connection) -> Operation {
+        return BlockOperation { _ = connection.write(self) }
     }
 }
 
-extension SequenceType where
-    Generator.Element: Persistable,
-    Generator.Element: ValueCoding,
-    Generator.Element.Coder: NSCoding,
-    Generator.Element.Coder.ValueType == Generator.Element {
+extension Sequence where
+    Iterator.Element: Persistable,
+    Iterator.Element: ValueCoding,
+    Iterator.Element.Coder: NSCoding,
+    Iterator.Element.Coder.Value == Iterator.Element {
 
     /**
     Write the items using an existing transaction.
@@ -71,7 +71,7 @@ extension SequenceType where
     - parameter transaction: a WriteTransactionType e.g. YapDatabaseReadWriteTransaction
     - returns: the receiver.
     */
-    public func write<WriteTransaction: WriteTransactionType>(transaction: WriteTransaction) -> [Generator.Element] {
+    public func write<WriteTransaction: WriteTransactionType>(_ transaction: WriteTransaction) -> [Iterator.Element] {
         return transaction.write(self)
     }
 
@@ -81,7 +81,7 @@ extension SequenceType where
     - parameter connection: a ConnectionType e.g. YapDatabaseConnection
     - returns: the receiver.
     */
-    public func write<Connection: ConnectionType>(connection: Connection) -> [Generator.Element] {
+    public func write<Connection: ConnectionType>(_ connection: Connection) -> [Iterator.Element] {
         return connection.write(self)
     }
 
@@ -91,7 +91,7 @@ extension SequenceType where
     - parameter connection: a ConnectionType e.g. YapDatabaseConnection
     - returns: a closure which receives as an argument the receiver of this function.
     */
-    public func asyncWrite<Connection: ConnectionType>(connection: Connection, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: ([Generator.Element] -> Void)? = .None) {
+    public func asyncWrite<Connection: ConnectionType>(_ connection: Connection, queue: DispatchQueue = DispatchQueue.main, completion: (([Iterator.Element]) -> Void)? = .none) {
         return connection.asyncWrite(self, queue: queue, completion: completion)
     }
 
@@ -101,8 +101,8 @@ extension SequenceType where
     - parameter connection: a YapDatabaseConnection
     - returns: an `NSOperation`
     */
-    public func writeOperation<Connection: ConnectionType>(connection: Connection) -> NSOperation {
-        return NSBlockOperation { connection.write(self) }
+    public func writeOperation<Connection: ConnectionType>(_ connection: Connection) -> Operation {
+        return BlockOperation { _ = connection.write(self) }
     }
 }
 
@@ -112,45 +112,45 @@ extension Readable where
     ItemType: ValueCoding,
     ItemType: Persistable,
     ItemType.Coder: NSCoding,
-    ItemType.Coder.ValueType == ItemType {
+    ItemType.Coder.Value == ItemType {
 
-    func inTransaction(transaction: Database.Connection.ReadTransaction, atIndex index: YapDB.Index) -> ItemType? {
+    func inTransaction(_ transaction: Database.Connection.ReadTransaction, atIndex index: YapDB.Index) -> ItemType? {
         return transaction.readAtIndex(index)
     }
 
-    func inTransactionAtIndex(transaction: Database.Connection.ReadTransaction) -> YapDB.Index -> ItemType? {
+    func inTransactionAtIndex(_ transaction: Database.Connection.ReadTransaction) -> (YapDB.Index) -> ItemType? {
         return { self.inTransaction(transaction, atIndex: $0) }
     }
 
-    func atIndexInTransaction(index: YapDB.Index) -> Database.Connection.ReadTransaction -> ItemType? {
+    func atIndexInTransaction(_ index: YapDB.Index) -> (Database.Connection.ReadTransaction) -> ItemType? {
         return { self.inTransaction($0, atIndex: index) }
     }
 
     func atIndexesInTransaction<
-        Indexes where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index>(indexes: Indexes) -> Database.Connection.ReadTransaction -> [ItemType] {
+        Indexes>(_ indexes: Indexes) -> (Database.Connection.ReadTransaction) -> [ItemType?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index {
             let atIndex = inTransactionAtIndex
-            return { indexes.flatMap(atIndex($0)) }
+            return { indexes.map(atIndex($0)) }
     }
 
-    func inTransaction(transaction: Database.Connection.ReadTransaction, byKey key: String) -> ItemType? {
+    func inTransaction(_ transaction: Database.Connection.ReadTransaction, byKey key: String) -> ItemType? {
         return inTransaction(transaction, atIndex: ItemType.indexWithKey(key))
     }
 
-    func inTransactionByKey(transaction: Database.Connection.ReadTransaction) -> String -> ItemType? {
+    func inTransactionByKey(_ transaction: Database.Connection.ReadTransaction) -> (String) -> ItemType? {
         return { self.inTransaction(transaction, byKey: $0) }
     }
 
-    func byKeyInTransaction(key: String) -> Database.Connection.ReadTransaction -> ItemType? {
+    func byKeyInTransaction(_ key: String) -> (Database.Connection.ReadTransaction) -> ItemType? {
         return { self.inTransaction($0, byKey: key) }
     }
 
-    func byKeysInTransaction(keys: [String]? = .None) -> Database.Connection.ReadTransaction -> [ItemType] {
+    func byKeysInTransaction(_ keys: [String]? = .none) -> (Database.Connection.ReadTransaction) -> [ItemType?] {
         let byKey = inTransactionByKey
         return { transaction in
             let keys = keys ?? transaction.keysInCollection(ItemType.collection)
-            return keys.flatMap(byKey(transaction))
+            return keys.map(byKey(transaction))
         }
     }
 
@@ -160,7 +160,7 @@ extension Readable where
     - parameter index: a YapDB.Index
     - returns: an optional `ItemType`
     */
-    public func atIndex(index: YapDB.Index) -> ItemType? {
+    public func atIndex(_ index: YapDB.Index) -> ItemType? {
         return sync(atIndexInTransaction(index))
     }
 
@@ -171,9 +171,9 @@ extension Readable where
     - returns: an array of `ItemType`
     */
     public func atIndexes<
-        Indexes where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index>(indexes: Indexes) -> [ItemType] {
+        Indexes>(_ indexes: Indexes) -> [ItemType?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index {
             return sync(atIndexesInTransaction(indexes))
     }
 
@@ -183,7 +183,7 @@ extension Readable where
     - parameter key: a String
     - returns: an optional `ItemType`
     */
-    public func byKey(key: String) -> ItemType? {
+    public func byKey(_ key: String) -> ItemType? {
         return sync(byKeyInTransaction(key))
     }
 
@@ -194,9 +194,9 @@ extension Readable where
     - returns: an array of `ItemType`
     */
     public func byKeys<
-        Keys where
-        Keys: SequenceType,
-        Keys.Generator.Element == String>(keys: Keys) -> [ItemType] {
+        Keys>(_ keys: Keys) -> [ItemType?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String {
             return sync(byKeysInTransaction(Array(keys)))
     }
 
@@ -205,7 +205,7 @@ extension Readable where
 
     - returns: an array of `ItemType`
     */
-    public func all() -> [ItemType] {
+    public func all() -> [ItemType?] {
         return sync(byKeysInTransaction())
     }
 
@@ -215,12 +215,18 @@ extension Readable where
     - parameter keys: a SequenceType of String values
     - returns: a tuple of type `([ItemType], [String])`
     */
-    public func filterExisting(keys: [String]) -> (existing: [ItemType], missing: [String]) {
+    public func filterExisting(_ keys: [String]) -> (existing: [ItemType], missing: [String]) {
         let existingInTransaction = byKeysInTransaction(keys)
         return sync { transaction -> ([ItemType], [String]) in
-            let existing = existingInTransaction(transaction)
-            let existingKeys = existing.map(keyForPersistable)
-            let missingKeys = keys.filter { !existingKeys.contains($0) }
+            var missingKeys = [String]()
+            let maybeExisting = existingInTransaction(transaction)
+            let existing = zip(keys, maybeExisting).flatMap { zipped -> ItemType? in
+                guard let item = zipped.1 else {
+                    missingKeys.append(zipped.0)
+                    return nil
+                }
+                return item
+            }
             return (existing, missingKeys)
         }
     }
diff --git a/Sources/Persistable_ValueWithObjectMetadata.swift b/Sources/Persistable_ValueWithObjectMetadata.swift
index bbabc82..4af8229 100644
--- a/Sources/Persistable_ValueWithObjectMetadata.swift
+++ b/Sources/Persistable_ValueWithObjectMetadata.swift
@@ -14,7 +14,7 @@ import ValueCoding
 extension Persistable where
     Self: ValueCoding,
     Self.Coder: NSCoding,
-    Self.Coder.ValueType == Self {
+    Self.Coder.Value == Self {
 
     // Writing
 
@@ -25,9 +25,9 @@ extension Persistable where
     - returns: the receiver.
     */
     public func writeWithMetadata<
-        WriteTransaction, Metadata where
+        WriteTransaction, Metadata>(_ transaction: WriteTransaction, metadata: Metadata?) -> YapItem<Self, Metadata> where
         WriteTransaction: WriteTransactionType,
-        Metadata: NSCoding>(transaction: WriteTransaction, metadata: Metadata?) -> YapItem<Self, Metadata> {
+        Metadata: NSCoding {
         return transaction.writeWithMetadata(YapItem(self, metadata))
     }
 
@@ -38,9 +38,9 @@ extension Persistable where
     - returns: the receiver.
     */
     public func writeWithMetadata<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: Metadata?) -> YapItem<Self, Metadata> where
         Connection: ConnectionType,
-        Metadata: NSCoding>(connection: Connection, metadata: Metadata?) -> YapItem<Self, Metadata> {
+        Metadata: NSCoding {
         return connection.writeWithMetadata(YapItem(self, metadata))
     }
 
@@ -51,9 +51,9 @@ extension Persistable where
     - returns: a closure which receives as an argument the receiver of this function.
     */
     public func asyncWriteWithMetadata<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: Metadata?, queue: DispatchQueue = DispatchQueue.main, completion: ((YapItem<Self, Metadata>) -> Void)? = .none) where
         Connection: ConnectionType,
-        Metadata: NSCoding>(connection: Connection, metadata: Metadata?, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: (YapItem<Self, Metadata> -> Void)? = .None) {
+        Metadata: NSCoding {
         return connection.asyncWriteWithMetadata(YapItem(self, metadata), queue: queue, completion: completion)
     }
 
@@ -64,18 +64,18 @@ extension Persistable where
     - returns: an `NSOperation`
     */
     public func writeWithMetadataOperation<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: Metadata?) -> Operation where
         Connection: ConnectionType,
-        Metadata: NSCoding>(connection: Connection, metadata: Metadata?) -> NSOperation {
-        return NSBlockOperation { connection.writeWithMetadata(YapItem(self, metadata)) }
+        Metadata: NSCoding {
+        return BlockOperation { _ = connection.writeWithMetadata(YapItem(self, metadata)) }
     }
 }
 
-extension SequenceType where
-    Generator.Element: Persistable,
-    Generator.Element: ValueCoding,
-    Generator.Element.Coder: NSCoding,
-    Generator.Element.Coder.ValueType == Generator.Element {
+extension Sequence where
+    Iterator.Element: Persistable,
+    Iterator.Element: ValueCoding,
+    Iterator.Element.Coder: NSCoding,
+    Iterator.Element.Coder.Value == Iterator.Element {
 
     /**
      Zips the receiver with metadata into an array of YapItem.
@@ -85,10 +85,10 @@ extension SequenceType where
      - returns: an array where Persistables and Metadata with corresponding indexes in `self` and `metadata` are joined in a `YapItem`
      */
     public func yapItems<
-        Metadatas, Metadata where
+        Metadatas, Metadata>(with metadata: Metadatas) -> [YapItem<Iterator.Element, Metadata>] where
         Metadata: NSCoding,
-        Metadatas: SequenceType,
-        Metadatas.Generator.Element == Optional<Metadata>>(with metadata: Metadatas) -> [YapItem<Generator.Element, Metadata>] {
+        Metadatas: Sequence,
+        Metadatas.Iterator.Element == Optional<Metadata> {
         return zip(self, metadata).map { YapItem($0, $1) }
     }
 
@@ -99,9 +99,9 @@ extension SequenceType where
     - returns: the receiver.
     */
     public func writeWithMetadata<
-        WriteTransaction, Metadata where
+        WriteTransaction, Metadata>(_ transaction: WriteTransaction, metadata: [Metadata?]) -> [YapItem<Iterator.Element, Metadata>] where
         WriteTransaction: WriteTransactionType,
-        Metadata: NSCoding>(transaction: WriteTransaction, metadata: [Metadata?]) -> [YapItem<Generator.Element, Metadata>] {
+        Metadata: NSCoding {
         let items = yapItems(with: metadata)
         return transaction.writeWithMetadata(items)
     }
@@ -113,9 +113,9 @@ extension SequenceType where
     - returns: the receiver.
     */
     public func writeWithMetadata<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: [Metadata?]) -> [YapItem<Iterator.Element, Metadata>] where
         Connection: ConnectionType,
-        Metadata: NSCoding>(connection: Connection, metadata: [Metadata?]) -> [YapItem<Generator.Element, Metadata>] {
+        Metadata: NSCoding {
         let items = yapItems(with: metadata)
         return connection.writeWithMetadata(items)
     }
@@ -127,9 +127,9 @@ extension SequenceType where
     - returns: a closure which receives as an argument the receiver of this function.
     */
     public func asyncWriteWithMetadata<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: [Metadata?], queue: DispatchQueue = DispatchQueue.main, completion: (([YapItem<Iterator.Element, Metadata>]) -> Void)? = .none) where
         Connection: ConnectionType,
-        Metadata: NSCoding>(connection: Connection, metadata: [Metadata?], queue: dispatch_queue_t = dispatch_get_main_queue(), completion: ([YapItem<Generator.Element, Metadata>] -> Void)? = .None) {
+        Metadata: NSCoding {
         let items = yapItems(with: metadata)
         return connection.asyncWriteWithMetadata(items, queue: queue, completion: completion)
     }
@@ -141,11 +141,11 @@ extension SequenceType where
     - returns: an `NSOperation`
     */
     public func writeWithMetadataOperation<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: [Metadata?]) -> Operation where
         Connection: ConnectionType,
-        Metadata: NSCoding>(connection: Connection, metadata: [Metadata?]) -> NSOperation {
+        Metadata: NSCoding {
         let items = yapItems(with: metadata)
-        return NSBlockOperation { connection.writeWithMetadata(items) }
+        return BlockOperation { _ = connection.writeWithMetadata(items) }
     }
 }
 
@@ -156,44 +156,44 @@ extension Readable where
     ItemType: ValueCoding,
     ItemType: Persistable,
     ItemType.Coder: NSCoding,
-    ItemType.Coder.ValueType == ItemType {
+    ItemType.Coder.Value == ItemType {
 
-    func withMetadataInTransaction<Metadata: NSCoding>(transaction: Database.Connection.ReadTransaction, atIndex index: YapDB.Index) -> YapItem<ItemType, Metadata>? {
+    func withMetadataInTransaction<Metadata: NSCoding>(_ transaction: Database.Connection.ReadTransaction, atIndex index: YapDB.Index) -> YapItem<ItemType, Metadata>? {
         return transaction.readWithMetadataAtIndex(index)
     }
 
-    func withMetadataInTransactionAtIndex<Metadata: NSCoding>(transaction: Database.Connection.ReadTransaction) -> YapDB.Index -> YapItem<ItemType, Metadata>? {
+    func withMetadataInTransactionAtIndex<Metadata: NSCoding>(_ transaction: Database.Connection.ReadTransaction) -> (YapDB.Index) -> YapItem<ItemType, Metadata>? {
         return { self.withMetadataInTransaction(transaction, atIndex: $0) }
     }
 
-    func withMetadataAtIndexInTransaction<Metadata: NSCoding>(index: YapDB.Index) -> Database.Connection.ReadTransaction -> YapItem<ItemType, Metadata>? {
+    func withMetadataAtIndexInTransaction<Metadata: NSCoding>(_ index: YapDB.Index) -> (Database.Connection.ReadTransaction) -> YapItem<ItemType, Metadata>? {
         return { self.withMetadataInTransaction($0, atIndex: index) }
     }
 
     func withMetadataAtIndexesInTransaction<
-        Indexes, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
-        Metadata: NSCoding>(indexes: Indexes) -> Database.Connection.ReadTransaction -> [YapItem<ItemType, Metadata>] {
-            return { indexes.flatMap(self.withMetadataInTransactionAtIndex($0)) }
+        Indexes, Metadata>(_ indexes: Indexes) -> (Database.Connection.ReadTransaction) -> [YapItem<ItemType, Metadata>?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
+        Metadata: NSCoding {
+            return { indexes.map(self.withMetadataInTransactionAtIndex($0)) }
     }
 
-    func withMetadataInTransaction<Metadata: NSCoding>(transaction: Database.Connection.ReadTransaction, byKey key: String) -> YapItem<ItemType, Metadata>? {
+    func withMetadataInTransaction<Metadata: NSCoding>(_ transaction: Database.Connection.ReadTransaction, byKey key: String) -> YapItem<ItemType, Metadata>? {
         return withMetadataInTransaction(transaction, atIndex: ItemType.indexWithKey(key))
     }
 
-    func withMetadataInTransactionByKey<Metadata: NSCoding>(transaction: Database.Connection.ReadTransaction) -> String -> YapItem<ItemType, Metadata>? {
+    func withMetadataInTransactionByKey<Metadata: NSCoding>(_ transaction: Database.Connection.ReadTransaction) -> (String) -> YapItem<ItemType, Metadata>? {
         return { self.withMetadataInTransaction(transaction, byKey: $0) }
     }
 
-    func withMetadataByKeyInTransaction<Metadata: NSCoding>(key: String) -> Database.Connection.ReadTransaction -> YapItem<ItemType, Metadata>? {
+    func withMetadataByKeyInTransaction<Metadata: NSCoding>(_ key: String) -> (Database.Connection.ReadTransaction) -> YapItem<ItemType, Metadata>? {
         return { self.withMetadataInTransaction($0, byKey: key) }
     }
 
-    func withMetadataByKeysInTransaction<Metadata: NSCoding>(keys: [String]? = .None) -> Database.Connection.ReadTransaction -> [YapItem<ItemType, Metadata>] {
+    func withMetadataByKeysInTransaction<Metadata: NSCoding>(_ keys: [String]? = .none) -> (Database.Connection.ReadTransaction) -> [YapItem<ItemType, Metadata>?] {
         return { transaction in
             let keys = keys ?? transaction.keysInCollection(ItemType.collection)
-            return keys.flatMap(self.withMetadataInTransactionByKey(transaction))
+            return keys.map(self.withMetadataInTransactionByKey(transaction))
         }
     }
 
@@ -203,7 +203,7 @@ extension Readable where
     - parameter index: a YapDB.Index
     - returns: an optional `ItemType`
     */
-    public func withMetadataAtIndex<Metadata: NSCoding>(index: YapDB.Index) -> YapItem<ItemType, Metadata>? {
+    public func withMetadataAtIndex<Metadata: NSCoding>(_ index: YapDB.Index) -> YapItem<ItemType, Metadata>? {
         return sync(withMetadataAtIndexInTransaction(index))
     }
 
@@ -214,10 +214,10 @@ extension Readable where
     - returns: an array of `ItemType`
     */
     public func withMetadataAtIndexes<
-        Indexes, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
-        Metadata: NSCoding>(indexes: Indexes) -> [YapItem<ItemType, Metadata>] {
+        Indexes, Metadata>(_ indexes: Indexes) -> [YapItem<ItemType, Metadata>?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
+        Metadata: NSCoding {
             return sync(withMetadataAtIndexesInTransaction(indexes))
     }
 
@@ -227,7 +227,7 @@ extension Readable where
     - parameter key: a String
     - returns: an optional `ItemType`
     */
-    public func withMetadataByKey<Metadata: NSCoding>(key: String) -> YapItem<ItemType, Metadata>? {
+    public func withMetadataByKey<Metadata: NSCoding>(_ key: String) -> YapItem<ItemType, Metadata>? {
         return sync(withMetadataByKeyInTransaction(key))
     }
 
@@ -238,10 +238,10 @@ extension Readable where
     - returns: an array of `ItemType`
     */
     public func withMetadataByKeys<
-        Keys, Metadata where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
-        Metadata: NSCoding>(keys: Keys) -> [YapItem<ItemType, Metadata>] {
+        Keys, Metadata>(_ keys: Keys) -> [YapItem<ItemType, Metadata>?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
+        Metadata: NSCoding {
             return sync(withMetadataByKeysInTransaction(Array(keys)))
     }
 
@@ -250,7 +250,7 @@ extension Readable where
 
     - returns: an array of `ItemType`
     */
-    public func withMetadataAll<Metadata: NSCoding>() -> [YapItem<ItemType, Metadata>] {
+    public func withMetadataAll<Metadata: NSCoding>() -> [YapItem<ItemType, Metadata>?] {
         return sync(withMetadataByKeysInTransaction())
     }
 
@@ -260,12 +260,18 @@ extension Readable where
     - parameter keys: a SequenceType of String values
     - returns: a tuple of type `([ItemType], [String])`
     */
-    public func withMetadataFilterExisting<Metadata: NSCoding>(keys: [String]) -> (existing: [YapItem<ItemType, Metadata>], missing: [String]) {
-        let existingInTransaction: Database.Connection.ReadTransaction -> [YapItem<ItemType, Metadata>] = withMetadataByKeysInTransaction(keys)
+    public func withMetadataFilterExisting<Metadata: NSCoding>(_ keys: [String]) -> (existing: [YapItem<ItemType, Metadata>], missing: [String]) {
+        let existingInTransaction: (Database.Connection.ReadTransaction) -> [YapItem<ItemType, Metadata>?] = withMetadataByKeysInTransaction(keys)
         return sync { transaction -> ([YapItem<ItemType, Metadata>], [String]) in
-            let existing = existingInTransaction(transaction)
-            let existingKeys = existing.map {keyForPersistable($0.value)}
-            let missingKeys = keys.filter { !existingKeys.contains($0) }
+            var missingKeys = [String]()
+            let maybeExisting = existingInTransaction(transaction)
+            let existing = zip(keys, maybeExisting).flatMap { zipped -> YapItem<ItemType, Metadata>? in
+                guard let item = zipped.1 else {
+                    missingKeys.append(zipped.0)
+                    return nil
+                }
+                return item
+            }
             return (existing, missingKeys)
         }
     }
diff --git a/Sources/Persistable_ValueWithValueMetadata.swift b/Sources/Persistable_ValueWithValueMetadata.swift
index c7c4912..4d60aff 100644
--- a/Sources/Persistable_ValueWithValueMetadata.swift
+++ b/Sources/Persistable_ValueWithValueMetadata.swift
@@ -14,7 +14,7 @@ import ValueCoding
 extension Persistable where
     Self: ValueCoding,
     Self.Coder: NSCoding,
-    Self.Coder.ValueType == Self {
+    Self.Coder.Value == Self {
 
     // Writing
 
@@ -25,11 +25,11 @@ extension Persistable where
     - returns: the receiver.
     */
     public func writeWithMetadata<
-        WriteTransaction, Metadata where
+        WriteTransaction, Metadata>(_ transaction: WriteTransaction, metadata: Metadata?) -> YapItem<Self, Metadata> where
         WriteTransaction: WriteTransactionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(transaction: WriteTransaction, metadata: Metadata?) -> YapItem<Self, Metadata> {
+        Metadata.Coder.Value == Metadata {
         return transaction.writeWithMetadata(YapItem(self, metadata))
     }
 
@@ -40,11 +40,11 @@ extension Persistable where
     - returns: the receiver.
     */
     public func writeWithMetadata<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: Metadata?) -> YapItem<Self, Metadata> where
         Connection: ConnectionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(connection: Connection, metadata: Metadata?) -> YapItem<Self, Metadata> {
+        Metadata.Coder.Value == Metadata {
         return connection.writeWithMetadata(YapItem(self, metadata))
     }
 
@@ -55,11 +55,11 @@ extension Persistable where
     - returns: a closure which receives as an argument the receiver of this function.
     */
     public func asyncWriteWithMetadata<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: Metadata?, queue: DispatchQueue = DispatchQueue.main, completion: ((YapItem<Self, Metadata>) -> Void)? = .none) where
         Connection: ConnectionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(connection: Connection, metadata: Metadata?, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: (YapItem<Self, Metadata> -> Void)? = .None) {
+        Metadata.Coder.Value == Metadata {
         return connection.asyncWriteWithMetadata(YapItem(self, metadata), queue: queue, completion: completion)
     }
 
@@ -70,20 +70,20 @@ extension Persistable where
     - returns: an `NSOperation`
     */
     public func writeWithMetadataOperation<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: Metadata?) -> Operation where
         Connection: ConnectionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(connection: Connection, metadata: Metadata?) -> NSOperation {
-        return NSBlockOperation { connection.writeWithMetadata(YapItem(self, metadata)) }
+        Metadata.Coder.Value == Metadata {
+        return BlockOperation { _ = connection.writeWithMetadata(YapItem(self, metadata)) }
     }
 }
 
-extension SequenceType where
-    Generator.Element: Persistable,
-    Generator.Element: ValueCoding,
-    Generator.Element.Coder: NSCoding,
-    Generator.Element.Coder.ValueType == Generator.Element {
+extension Sequence where
+    Iterator.Element: Persistable,
+    Iterator.Element: ValueCoding,
+    Iterator.Element.Coder: NSCoding,
+    Iterator.Element.Coder.Value == Iterator.Element {
 
     /**
      Zips the receiver with metadata into an array of YapItem.
@@ -93,12 +93,12 @@ extension SequenceType where
      - returns: an array where Persistables and Metadata with corresponding indexes in `self` and `metadata` are joined in a `YapItem`
      */
     public func yapItems<
-        Metadatas, Metadata where
+        Metadatas, Metadata>(with metadata: Metadatas) -> [YapItem<Iterator.Element, Metadata>] where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata,
-        Metadatas: SequenceType,
-        Metadatas.Generator.Element == Optional<Metadata>>(with metadata: Metadatas) -> [YapItem<Generator.Element, Metadata>] {
+        Metadata.Coder.Value == Metadata,
+        Metadatas: Sequence,
+        Metadatas.Iterator.Element == Optional<Metadata> {
         return zip(self, metadata).map { YapItem($0, $1) }
     }
 
@@ -109,11 +109,11 @@ extension SequenceType where
     - returns: the receiver.
     */
     public func writeWithMetadata<
-        WriteTransaction, Metadata where
+        WriteTransaction, Metadata>(_ transaction: WriteTransaction, metadata: [Metadata?]) -> [YapItem<Iterator.Element, Metadata>] where
         WriteTransaction: WriteTransactionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(transaction: WriteTransaction, metadata: [Metadata?]) -> [YapItem<Generator.Element, Metadata>] {
+        Metadata.Coder.Value == Metadata {
         let items = yapItems(with: metadata)
         return transaction.writeWithMetadata(items)
     }
@@ -125,11 +125,11 @@ extension SequenceType where
     - returns: the receiver.
     */
     public func writeWithMetadata<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: [Metadata?]) -> [YapItem<Iterator.Element, Metadata>] where
         Connection: ConnectionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(connection: Connection, metadata: [Metadata?]) -> [YapItem<Generator.Element, Metadata>] {
+        Metadata.Coder.Value == Metadata {
         let items = yapItems(with: metadata)
         return connection.writeWithMetadata(items)
     }
@@ -141,11 +141,11 @@ extension SequenceType where
     - returns: a closure which receives as an argument the receiver of this function.
     */
     public func asyncWriteWithMetadata<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: [Metadata?], queue: DispatchQueue = DispatchQueue.main, completion: (([YapItem<Iterator.Element, Metadata>]) -> Void)? = .none) where
         Connection: ConnectionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(connection: Connection, metadata: [Metadata?], queue: dispatch_queue_t = dispatch_get_main_queue(), completion: ([YapItem<Generator.Element, Metadata>] -> Void)? = .None) {
+        Metadata.Coder.Value == Metadata {
         let items = yapItems(with: metadata)
         return connection.asyncWriteWithMetadata(items, queue: queue, completion: completion)
     }
@@ -157,13 +157,13 @@ extension SequenceType where
     - returns: an `NSOperation`
     */
     public func writeWithMetadataOperation<
-        Connection, Metadata where
+        Connection, Metadata>(_ connection: Connection, metadata: [Metadata?]) -> Operation where
         Connection: ConnectionType,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(connection: Connection, metadata: [Metadata?]) -> NSOperation {
+        Metadata.Coder.Value == Metadata {
         let items = yapItems(with: metadata)
-        return NSBlockOperation { connection.writeWithMetadata(items) }
+        return BlockOperation { _ = connection.writeWithMetadata(items) }
     }
 }
 
@@ -173,74 +173,74 @@ extension Readable where
     ItemType: ValueCoding,
     ItemType: Persistable,
     ItemType.Coder: NSCoding,
-    ItemType.Coder.ValueType == ItemType {
+    ItemType.Coder.Value == ItemType {
 
     func withMetadataInTransaction<
-        Metadata where
+        Metadata>(_ transaction: Database.Connection.ReadTransaction, atIndex index: YapDB.Index) -> YapItem<ItemType, Metadata>? where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(transaction: Database.Connection.ReadTransaction, atIndex index: YapDB.Index) -> YapItem<ItemType, Metadata>? {
+        Metadata.Coder.Value == Metadata {
         return transaction.readWithMetadataAtIndex(index)
     }
 
     func withMetadataInTransactionAtIndex<
-        Metadata where
+        Metadata>(_ transaction: Database.Connection.ReadTransaction) -> (YapDB.Index) -> YapItem<ItemType, Metadata>? where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(transaction: Database.Connection.ReadTransaction) -> YapDB.Index -> YapItem<ItemType, Metadata>? {
+        Metadata.Coder.Value == Metadata {
         return { self.withMetadataInTransaction(transaction, atIndex: $0) }
     }
 
     func withMetadataAtIndexInTransaction<
-        Metadata where
+        Metadata>(_ index: YapDB.Index) -> (Database.Connection.ReadTransaction) -> YapItem<ItemType, Metadata>? where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(index: YapDB.Index) -> Database.Connection.ReadTransaction -> YapItem<ItemType, Metadata>? {
+        Metadata.Coder.Value == Metadata {
         return { self.withMetadataInTransaction($0, atIndex: index) }
     }
 
     func withMetadataAtIndexesInTransaction<
-        Indexes, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, Metadata>(_ indexes: Indexes) -> (Database.Connection.ReadTransaction) -> [YapItem<ItemType, Metadata>?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(indexes: Indexes) -> Database.Connection.ReadTransaction -> [YapItem<ItemType, Metadata>] {
-        return { indexes.flatMap(self.withMetadataInTransactionAtIndex($0)) }
+        Metadata.Coder.Value == Metadata {
+        return { indexes.map(self.withMetadataInTransactionAtIndex($0)) }
     }
 
     func withMetadataInTransaction<
-        Metadata where
+        Metadata>(_ transaction: Database.Connection.ReadTransaction, byKey key: String) -> YapItem<ItemType, Metadata>? where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(transaction: Database.Connection.ReadTransaction, byKey key: String) -> YapItem<ItemType, Metadata>? {
+        Metadata.Coder.Value == Metadata {
         return withMetadataInTransaction(transaction, atIndex: ItemType.indexWithKey(key))
     }
 
     func withMetadataInTransactionByKey<
-        Metadata where
+        Metadata>(_ transaction: Database.Connection.ReadTransaction) -> (String) -> YapItem<ItemType, Metadata>? where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(transaction: Database.Connection.ReadTransaction) -> String -> YapItem<ItemType, Metadata>? {
+        Metadata.Coder.Value == Metadata {
         return { self.withMetadataInTransaction(transaction, byKey: $0) }
     }
 
     func withMetadataByKeyInTransaction<
-        Metadata where
+        Metadata>(_ key: String) -> (Database.Connection.ReadTransaction) -> YapItem<ItemType, Metadata>? where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(key: String) -> Database.Connection.ReadTransaction -> YapItem<ItemType, Metadata>? {
+        Metadata.Coder.Value == Metadata {
         return { self.withMetadataInTransaction($0, byKey: key) }
     }
 
     func withMetadataByKeysInTransaction<
-        Metadata where
+        Metadata>(_ keys: [String]? = .none) -> (Database.Connection.ReadTransaction) -> [YapItem<ItemType, Metadata>?] where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(keys: [String]? = .None) -> Database.Connection.ReadTransaction -> [YapItem<ItemType, Metadata>] {
+        Metadata.Coder.Value == Metadata {
         return { transaction in
             let keys = keys ?? transaction.keysInCollection(ItemType.collection)
-            return keys.flatMap(self.withMetadataInTransactionByKey(transaction))
+            return keys.map(self.withMetadataInTransactionByKey(transaction))
         }
     }
 
@@ -251,10 +251,10 @@ extension Readable where
     - returns: an optional `ItemType`
     */
     public func withMetadataAtIndex<
-        Metadata where
+        Metadata>(_ index: YapDB.Index) -> YapItem<ItemType, Metadata>? where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(index: YapDB.Index) -> YapItem<ItemType, Metadata>? {
+        Metadata.Coder.Value == Metadata {
         return sync(withMetadataAtIndexInTransaction(index))
     }
 
@@ -265,12 +265,12 @@ extension Readable where
     - returns: an array of `ItemType`
     */
     public func withMetadataAtIndexes<
-        Indexes, Metadata where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index,
+        Indexes, Metadata>(_ indexes: Indexes) -> [YapItem<ItemType, Metadata>?] where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(indexes: Indexes) -> [YapItem<ItemType, Metadata>] {
+        Metadata.Coder.Value == Metadata {
             return sync(withMetadataAtIndexesInTransaction(indexes))
     }
 
@@ -281,10 +281,10 @@ extension Readable where
     - returns: an optional `ItemType`
     */
     public func withMetadataByKey<
-        Metadata where
+        Metadata>(_ key: String) -> YapItem<ItemType, Metadata>? where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(key: String) -> YapItem<ItemType, Metadata>? {
+        Metadata.Coder.Value == Metadata {
         return sync(withMetadataByKeyInTransaction(key))
     }
 
@@ -295,12 +295,12 @@ extension Readable where
     - returns: an array of `ItemType`
     */
     public func withMetadataByKeys<
-        Keys, Metadata where
-        Keys: SequenceType,
-        Keys.Generator.Element == String,
+        Keys, Metadata>(_ keys: Keys) -> [YapItem<ItemType, Metadata>?] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String,
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(keys: Keys) -> [YapItem<ItemType, Metadata>] {
+        Metadata.Coder.Value == Metadata {
             return sync(withMetadataByKeysInTransaction(Array(keys)))
     }
 
@@ -310,10 +310,10 @@ extension Readable where
     - returns: an array of `ItemType`
     */
     public func withMetadataAll<
-        Metadata where
+        Metadata>() -> [YapItem<ItemType, Metadata>?] where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>() -> [YapItem<ItemType, Metadata>] {
+        Metadata.Coder.Value == Metadata {
         return sync(withMetadataByKeysInTransaction())
     }
 
@@ -324,15 +324,21 @@ extension Readable where
     - returns: a tuple of type `([ItemType], [String])`
     */
     public func withMetadataFilterExisting<
-        Metadata where
+        Metadata>(_ keys: [String]) -> (existing: [YapItem<ItemType, Metadata>], missing: [String]) where
         Metadata: ValueCoding,
         Metadata.Coder: NSCoding,
-        Metadata.Coder.ValueType == Metadata>(keys: [String]) -> (existing: [YapItem<ItemType, Metadata>], missing: [String]) {
-        let existingInTransaction: Database.Connection.ReadTransaction -> [YapItem<ItemType, Metadata>] = withMetadataByKeysInTransaction(keys)
+        Metadata.Coder.Value == Metadata {
+        let existingInTransaction: (Database.Connection.ReadTransaction) -> [YapItem<ItemType, Metadata>?] = withMetadataByKeysInTransaction(keys)
         return sync { transaction -> ([YapItem<ItemType, Metadata>], [String]) in
-            let existing = existingInTransaction(transaction)
-            let existingKeys = existing.map {keyForPersistable($0.value)}
-            let missingKeys = keys.filter { !existingKeys.contains($0) }
+            var missingKeys = [String]()
+            let maybeExisting = existingInTransaction(transaction)
+            let existing = zip(keys, maybeExisting).flatMap { zipped -> YapItem<ItemType, Metadata>? in
+                guard let item = zipped.1 else {
+                    missingKeys.append(zipped.0)
+                    return nil
+                }
+                return item
+            }
             return (existing, missingKeys)
         }
     }
diff --git a/Sources/Read.swift b/Sources/Read.swift
index 4af4f59..d228c1f 100644
--- a/Sources/Read.swift
+++ b/Sources/Read.swift
@@ -26,17 +26,17 @@ public struct Read<Item, D: DatabaseType>: Readable {
     let reader: Handle<D>
 
     public var transaction: D.Connection.ReadTransaction? {
-        if case let .Transaction(transaction) = reader {
+        if case let .transaction(transaction) = reader {
             return transaction
         }
-        return .None
+        return .none
     }
 
     public var connection: D.Connection {
         switch reader {
-        case .Transaction(_):
+        case .transaction(_):
             fatalError("Attempting to get connection from a transaction.")
-        case .Connection(let connection):
+        case .connection(let connection):
             return connection
         default:
             return database.makeNewConnection()
@@ -44,22 +44,22 @@ public struct Read<Item, D: DatabaseType>: Readable {
     }
 
     internal var database: D {
-        if case let .Database(database) = reader {
+        if case let .database(database) = reader {
             return database
         }
         fatalError("Attempting to get database from \(reader)")
     }
 
     internal init(_ transaction: D.Connection.ReadTransaction) {
-        reader = .Transaction(transaction)
+        reader = .transaction(transaction)
     }
 
     internal init(_ connection: D.Connection) {
-        reader = .Connection(connection)
+        reader = .connection(connection)
     }
 
     internal init(_ database: D) {
-        reader = .Database(database)
+        reader = .database(database)
     }
 }
 
@@ -83,7 +83,7 @@ extension Persistable {
     - parameter transaction: a type conforming to ReadTransactionType such as
     YapDatabaseReadTransaction
     */
-    public static func read<D: DatabaseType>(transaction: D.Connection.ReadTransaction) -> Read<Self, D> {
+    public static func read<D: DatabaseType>(_ transaction: D.Connection.ReadTransaction) -> Read<Self, D> {
         return Read(transaction)
     }
 
@@ -105,11 +105,11 @@ extension Persistable {
     - parameter connection: a type conforming to ConnectionType such as
     YapDatabaseConnection.
     */
-    public static func read<D: DatabaseType>(connection: D.Connection) -> Read<Self, D> {
+    public static func read<D: DatabaseType>(_ connection: D.Connection) -> Read<Self, D> {
         return Read(connection)
     }
 
-    internal static func read<D: DatabaseType>(database: D) -> Read<Self, D> {
+    internal static func read<D: DatabaseType>(_ database: D) -> Read<Self, D> {
         return Read(database)
     }
 }
@@ -118,7 +118,7 @@ extension Readable
     where
     ItemType: Persistable {
 
-    func sync<T>(block: (Database.Connection.ReadTransaction) -> T) -> T {
+    func sync<T>(_ block: @escaping (Database.Connection.ReadTransaction) -> T) -> T {
         if let transaction = transaction {
             return block(transaction)
         }
diff --git a/Sources/YapDB.swift b/Sources/YapDB.swift
index 7534482..bfe133e 100644
--- a/Sources/YapDB.swift
+++ b/Sources/YapDB.swift
@@ -2,13 +2,19 @@
 //  Created by Daniel Thorpe on 22/04/2015.
 //
 
+import YapDatabase
+import YapDatabase.YapDatabaseView
+import YapDatabase.YapDatabaseFilteredView
+import YapDatabase.YapDatabaseFullTextSearch
+import YapDatabase.YapDatabaseSecondaryIndex
+
 protocol YapDatabaseViewProducer {
     func createDatabaseView() -> YapDatabaseView
 }
 
 protocol YapDatabaseExtensionRegistrar {
-    func isRegisteredInDatabase(database: YapDatabase) -> Bool
-    func registerInDatabase(database: YapDatabase, withConnection: YapDatabaseConnection?)
+    func isRegisteredInDatabase(_ database: YapDatabase) -> Bool
+    func registerInDatabase(_ database: YapDatabase, withConnection: YapDatabaseConnection?)
 }
 
 extension YapDB {
@@ -20,26 +26,26 @@ extension YapDB {
     */
     public enum Fetch: YapDatabaseExtensionRegistrar {
 
-        case View(YapDB.View)
-        case Filter(YapDB.Filter)
-        case Search(YapDB.SearchResults)
-        case Index(YapDB.SecondaryIndex)
+        case view(YapDB.View)
+        case filter(YapDB.Filter)
+        case search(YapDB.SearchResults)
+        case index(YapDB.SecondaryIndex)
 
         public var name: String {
             switch self {
-            case let .View(view):       return view.name
-            case let .Filter(filter):   return filter.name
-            case let .Search(search):   return search.name
-            case let .Index(index):     return index.name
+            case let .view(view):       return view.name
+            case let .filter(filter):   return filter.name
+            case let .search(search):   return search.name
+            case let .index(index):     return index.name
             }
         }
 
         var registrar: YapDatabaseExtensionRegistrar {
             switch self {
-            case let .View(view):       return view
-            case let .Filter(filter):   return filter
-            case let .Search(search):   return search
-            case let .Index(index):     return index
+            case let .view(view):       return view
+            case let .filter(filter):   return filter
+            case let .search(search):   return search
+            case let .index(index):     return index
             }
         }
 
@@ -49,7 +55,7 @@ extension YapDB {
         - parameter database: a YapDatabase instance
         - returns: a Bool
         */
-        public func isRegisteredInDatabase(database: YapDatabase) -> Bool {
+        public func isRegisteredInDatabase(_ database: YapDatabase) -> Bool {
             return registrar.isRegisteredInDatabase(database)
         }
 
@@ -59,7 +65,7 @@ extension YapDB {
         - parameter database: a YapDatabase instance
         - parameter connection: an optional YapDatabaseConnection, defaults to .None
         */
-        public func registerInDatabase(database: YapDatabase, withConnection connection: YapDatabaseConnection? = .None) {
+        public func registerInDatabase(_ database: YapDatabase, withConnection connection: YapDatabaseConnection? = .none) {
             registrar.registerInDatabase(database, withConnection: connection)
         }
 
@@ -69,7 +75,7 @@ extension YapDB {
         - parameter database: a YapDatabase instance
         - parameter connection: an optional YapDatabaseConnection, defaults to .None
         */
-        public func createViewMappings(mappings: Mappings, inDatabase database: YapDatabase, withConnection connection: YapDatabaseConnection? = .None) -> YapDatabaseViewMappings {
+        public func createViewMappings(_ mappings: Mappings, inDatabase database: YapDatabase, withConnection connection: YapDatabaseConnection? = .none) -> YapDatabaseViewMappings {
             registerInDatabase(database, withConnection: connection)
             return mappings.createMappingsWithViewName(name)
         }
@@ -78,13 +84,13 @@ extension YapDB {
 
 extension YapDB {
 
-    public class BaseExtension {
+    open class BaseExtension {
         let name: String
         let version: String
         let collections: Set<String>?
         let persistent: Bool
 
-        init(name n: String, version v: String = "1.0", persistent p: Bool = true, collections c: [String]? = .None) {
+        init(name n: String, version v: String = "1.0", persistent p: Bool = true, collections c: [String]? = .none) {
             name = n
             version = v
             persistent = p
@@ -97,15 +103,15 @@ extension YapDB {
         - parameter database: a YapDatabase instance
         - returns: A Bool
         */
-        public func isRegisteredInDatabase(database: YapDatabase) -> Bool {
-            return (database.registeredExtension(name) as? YapDatabaseView) != .None
+        public func isRegisteredInDatabase(_ database: YapDatabase) -> Bool {
+            return (database.registeredExtension(name) as? YapDatabaseExtension) != .none
         }
     }
 
     /**
     The base class for other YapDatabaseView wrapper types.
     */
-    public class BaseView: BaseExtension {
+    open class BaseView: BaseExtension {
 
         var options: YapDatabaseViewOptions {
             get {
@@ -124,7 +130,7 @@ extension YapDB {
     A wrapper around YapDatabaseView. It can be constructed with a name, which is
     the name the extension is registered under, a grouping enum type and a sorting enum type.
     */
-    public class View: BaseView, YapDatabaseViewProducer, YapDatabaseExtensionRegistrar {
+    open class View: BaseView, YapDatabaseViewProducer, YapDatabaseExtensionRegistrar {
 
         /**
         An enum to make creating YapDatabaseViewGrouping easier. E.g.
@@ -135,25 +141,25 @@ extension YapDB {
 
         */
         public enum Grouping {
-            case ByKey(YapDatabaseViewGroupingWithKeyBlock)
-            case ByObject(YapDatabaseViewGroupingWithObjectBlock)
-            case ByMetadata(YapDatabaseViewGroupingWithMetadataBlock)
-            case ByRow(YapDatabaseViewGroupingWithRowBlock)
+            case byKey(YapDatabaseViewGroupingWithKeyBlock)
+            case byObject(YapDatabaseViewGroupingWithObjectBlock)
+            case byMetadata(YapDatabaseViewGroupingWithMetadataBlock)
+            case byRow(YapDatabaseViewGroupingWithRowBlock)
 
-            func object(withOptions opts: YapDatabaseBlockInvoke? = .None) -> YapDatabaseViewGrouping {
+            func object(withOptions opts: YapDatabaseBlockInvoke? = .none) -> YapDatabaseViewGrouping {
                 if let opts = opts {
                     switch self {
-                    case let .ByKey(block):         return YapDatabaseViewGrouping.withOptions(opts, keyBlock: block)
-                    case let .ByObject(block):      return YapDatabaseViewGrouping.withOptions(opts, objectBlock: block)
-                    case let .ByMetadata(block):    return YapDatabaseViewGrouping.withOptions(opts, metadataBlock: block)
-                    case let .ByRow(block):         return YapDatabaseViewGrouping.withOptions(opts, rowBlock: block)
+                    case let .byKey(block):         return YapDatabaseViewGrouping.withOptions(opts, keyBlock: block)
+                    case let .byObject(block):      return YapDatabaseViewGrouping.withOptions(opts, objectBlock: block)
+                    case let .byMetadata(block):    return YapDatabaseViewGrouping.withOptions(opts, metadataBlock: block)
+                    case let .byRow(block):         return YapDatabaseViewGrouping.withOptions(opts, rowBlock: block)
                     }
                 } else {
                     switch self {
-                    case let .ByKey(block):         return YapDatabaseViewGrouping.withKeyBlock(block)
-                    case let .ByObject(block):      return YapDatabaseViewGrouping.withObjectBlock(block)
-                    case let .ByMetadata(block):    return YapDatabaseViewGrouping.withMetadataBlock(block)
-                    case let .ByRow(block):         return YapDatabaseViewGrouping.withRowBlock(block)
+                    case let .byKey(block):         return YapDatabaseViewGrouping.withKeyBlock(block)
+                    case let .byObject(block):      return YapDatabaseViewGrouping.withObjectBlock(block)
+                    case let .byMetadata(block):    return YapDatabaseViewGrouping.withMetadataBlock(block)
+                    case let .byRow(block):         return YapDatabaseViewGrouping.withRowBlock(block)
                     }
                 }
             }
@@ -163,25 +169,25 @@ extension YapDB {
         An enum to make creating YapDatabaseViewSorting easier.
         */
         public enum Sorting {
-            case ByKey(YapDatabaseViewSortingWithKeyBlock)
-            case ByObject(YapDatabaseViewSortingWithObjectBlock)
-            case ByMetadata(YapDatabaseViewSortingWithMetadataBlock)
-            case ByRow(YapDatabaseViewSortingWithRowBlock)
+            case byKey(YapDatabaseViewSortingWithKeyBlock)
+            case byObject(YapDatabaseViewSortingWithObjectBlock)
+            case byMetadata(YapDatabaseViewSortingWithMetadataBlock)
+            case byRow(YapDatabaseViewSortingWithRowBlock)
 
-            func object(withOptions opts: YapDatabaseBlockInvoke? = .None) -> YapDatabaseViewSorting {
+            func object(withOptions opts: YapDatabaseBlockInvoke? = .none) -> YapDatabaseViewSorting {
                 if let opts = opts {
                     switch self {
-                    case let .ByKey(block):         return YapDatabaseViewSorting.withOptions(opts, keyBlock: block)
-                    case let .ByObject(block):      return YapDatabaseViewSorting.withOptions(opts, objectBlock: block)
-                    case let .ByMetadata(block):    return YapDatabaseViewSorting.withOptions(opts, metadataBlock: block)
-                    case let .ByRow(block):         return YapDatabaseViewSorting.withOptions(opts, rowBlock: block)
+                    case let .byKey(block):         return YapDatabaseViewSorting.withOptions(opts, keyBlock: block)
+                    case let .byObject(block):      return YapDatabaseViewSorting.withOptions(opts, objectBlock: block)
+                    case let .byMetadata(block):    return YapDatabaseViewSorting.withOptions(opts, metadataBlock: block)
+                    case let .byRow(block):         return YapDatabaseViewSorting.withOptions(opts, rowBlock: block)
                     }
                 } else {
                     switch self {
-                    case let .ByKey(block):         return YapDatabaseViewSorting.withKeyBlock(block)
-                    case let .ByObject(block):      return YapDatabaseViewSorting.withObjectBlock(block)
-                    case let .ByMetadata(block):    return YapDatabaseViewSorting.withMetadataBlock(block)
-                    case let .ByRow(block):         return YapDatabaseViewSorting.withRowBlock(block)
+                    case let .byKey(block):         return YapDatabaseViewSorting.withKeyBlock(block)
+                    case let .byObject(block):      return YapDatabaseViewSorting.withObjectBlock(block)
+                    case let .byMetadata(block):    return YapDatabaseViewSorting.withMetadataBlock(block)
+                    case let .byRow(block):         return YapDatabaseViewSorting.withRowBlock(block)
                     }
                 }
             }
@@ -203,9 +209,9 @@ extension YapDB {
         - parameter collections: an optional array of collections which is used to white list the collections searched when populating the view.
         */
         public init(name: String,
-                    grouping g: Grouping, groupingOptions go: YapDatabaseBlockInvoke? = .None,
-                             sorting s: Sorting, sortingOptions so: YapDatabaseBlockInvoke? = .None,
-                            version: String = "1.0", persistent: Bool = true, collections: [String]? = .None) {
+                    grouping g: Grouping, groupingOptions go: YapDatabaseBlockInvoke? = .none,
+                             sorting s: Sorting, sortingOptions so: YapDatabaseBlockInvoke? = .none,
+                            version: String = "1.0", persistent: Bool = true, collections: [String]? = .none) {
             grouping = g
             groupingOptions = go
             sorting = s
@@ -217,13 +223,13 @@ extension YapDB {
             return YapDatabaseView(grouping: grouping.object(withOptions: groupingOptions), sorting: sorting.object(withOptions: sortingOptions), versionTag: version, options: options)
         }
 
-        func registerInDatabase(database: YapDatabase, withConnection connection: YapDatabaseConnection? = .None) {
+        func registerInDatabase(_ database: YapDatabase, withConnection connection: YapDatabaseConnection? = .none) {
             if !isRegisteredInDatabase(database) {
                 if let connection = connection {
-                    database.registerExtension(createDatabaseView(), withName: name, connection: connection)
+                    database.register(createDatabaseView(), withName: name, connection: connection)
                 }
                 else {
-                    database.registerExtension(createDatabaseView(), withName: name)
+                    database.register(createDatabaseView(), withName: name)
                 }
             }
         }
@@ -240,31 +246,31 @@ extension YapDB {
     is a YapDB.Fetch type. This allows for filtering of other filters, and 
     even filtering of search results.
     */
-    public class Filter: BaseView, YapDatabaseViewProducer, YapDatabaseExtensionRegistrar {
+    open class Filter: BaseView, YapDatabaseViewProducer, YapDatabaseExtensionRegistrar {
 
         /**
         An enum to make creating YapDatabaseViewFiltering easier.
         */
         public enum Filtering {
-            case ByKey(YapDatabaseViewFilteringWithKeyBlock)
-            case ByObject(YapDatabaseViewFilteringWithObjectBlock)
-            case ByMetadata(YapDatabaseViewFilteringWithMetadataBlock)
-            case ByRow(YapDatabaseViewFilteringWithRowBlock)
+            case byKey(YapDatabaseViewFilteringWithKeyBlock)
+            case byObject(YapDatabaseViewFilteringWithObjectBlock)
+            case byMetadata(YapDatabaseViewFilteringWithMetadataBlock)
+            case byRow(YapDatabaseViewFilteringWithRowBlock)
 
-            func object(withOptions ops: YapDatabaseBlockInvoke? = .None) -> YapDatabaseViewFiltering {
+            func object(withOptions ops: YapDatabaseBlockInvoke? = .none) -> YapDatabaseViewFiltering {
                 if let ops = ops {
                     switch self {
-                    case .ByKey(let block):      return YapDatabaseViewFiltering.withOptions(ops, keyBlock: block)
-                    case .ByObject(let block):   return YapDatabaseViewFiltering.withOptions(ops, objectBlock: block)
-                    case .ByMetadata(let block): return YapDatabaseViewFiltering.withOptions(ops, metadataBlock: block)
-                    case .ByRow(let block):      return YapDatabaseViewFiltering.withOptions(ops, rowBlock: block)
+                    case .byKey(let block):      return YapDatabaseViewFiltering.withOptions(ops, keyBlock: block)
+                    case .byObject(let block):   return YapDatabaseViewFiltering.withOptions(ops, objectBlock: block)
+                    case .byMetadata(let block): return YapDatabaseViewFiltering.withOptions(ops, metadataBlock: block)
+                    case .byRow(let block):      return YapDatabaseViewFiltering.withOptions(ops, rowBlock: block)
                     }
                 } else {
                     switch self {
-                    case .ByKey(let block):      return YapDatabaseViewFiltering.withKeyBlock(block)
-                    case .ByObject(let block):   return YapDatabaseViewFiltering.withObjectBlock(block)
-                    case .ByMetadata(let block): return YapDatabaseViewFiltering.withMetadataBlock(block)
-                    case .ByRow(let block):      return YapDatabaseViewFiltering.withRowBlock(block)
+                    case .byKey(let block):      return YapDatabaseViewFiltering.withKeyBlock(block)
+                    case .byObject(let block):   return YapDatabaseViewFiltering.withObjectBlock(block)
+                    case .byMetadata(let block): return YapDatabaseViewFiltering.withMetadataBlock(block)
+                    case .byRow(let block):      return YapDatabaseViewFiltering.withRowBlock(block)
                     }
                 }
             }
@@ -284,8 +290,8 @@ extension YapDB {
         - parameter persistent: a Bool, defaults to true - meaning that the contents of the view will be stored in YapDatabase between launches.
         - parameter collections: an optional array of collections which is used to white list the collections searched when populating the view.
         */
-        public init(name: String, parent p: YapDB.Fetch, filtering f: Filtering, filteringOptions fo: YapDatabaseBlockInvoke? = .None,
-                    version: String = "1.0", persistent: Bool = true, collections: [String]? = .None) {
+        public init(name: String, parent p: YapDB.Fetch, filtering f: Filtering, filteringOptions fo: YapDatabaseBlockInvoke? = .none,
+                    version: String = "1.0", persistent: Bool = true, collections: [String]? = .none) {
             parent = p
             filtering = f
             filteringOptions = fo
@@ -296,14 +302,14 @@ extension YapDB {
             return YapDatabaseFilteredView(parentViewName: parent.name, filtering: filtering.object(withOptions: filteringOptions), versionTag: version, options: options)
         }
 
-        func registerInDatabase(database: YapDatabase, withConnection connection: YapDatabaseConnection? = .None) {
+        func registerInDatabase(_ database: YapDatabase, withConnection connection: YapDatabaseConnection? = .none) {
             if !isRegisteredInDatabase(database) {
                 parent.registerInDatabase(database, withConnection: connection)
                 if let connection = connection {
-                    database.registerExtension(createDatabaseView(), withName: name, connection: connection)
+                    database.register(createDatabaseView(), withName: name, connection: connection)
                 }
                 else {
-                    database.registerExtension(createDatabaseView(), withName: name)
+                    database.register(createDatabaseView(), withName: name)
                 }
             }
         }
@@ -320,23 +326,23 @@ extension YapDB {
     In this case, the parent is a YapDB.Fetch type. This
     allows for searching of other filters, and even searching inside search results.
     */
-    public class SearchResults: BaseView, YapDatabaseViewProducer, YapDatabaseExtensionRegistrar {
+    open class SearchResults: BaseView, YapDatabaseViewProducer, YapDatabaseExtensionRegistrar {
 
         /**
         An enum to make creating YapDatabaseFullTextSearchHandler easier.
         */
         public enum Handler {
-            case ByKey(YapDatabaseFullTextSearchWithKeyBlock)
-            case ByObject(YapDatabaseFullTextSearchWithObjectBlock)
-            case ByMetadata(YapDatabaseFullTextSearchWithMetadataBlock)
-            case ByRow(YapDatabaseFullTextSearchWithRowBlock)
+            case byKey(YapDatabaseFullTextSearchWithKeyBlock)
+            case byObject(YapDatabaseFullTextSearchWithObjectBlock)
+            case byMetadata(YapDatabaseFullTextSearchWithMetadataBlock)
+            case byRow(YapDatabaseFullTextSearchWithRowBlock)
 
             public var object: YapDatabaseFullTextSearchHandler {
                 switch self {
-                case let .ByKey(block):         return YapDatabaseFullTextSearchHandler.withKeyBlock(block)
-                case let .ByObject(block):      return YapDatabaseFullTextSearchHandler.withObjectBlock(block)
-                case let .ByMetadata(block):    return YapDatabaseFullTextSearchHandler.withMetadataBlock(block)
-                case let .ByRow(block):         return YapDatabaseFullTextSearchHandler.withRowBlock(block)
+                case let .byKey(block):         return YapDatabaseFullTextSearchHandler.withKeyBlock(block)
+                case let .byObject(block):      return YapDatabaseFullTextSearchHandler.withObjectBlock(block)
+                case let .byMetadata(block):    return YapDatabaseFullTextSearchHandler.withMetadataBlock(block)
+                case let .byRow(block):         return YapDatabaseFullTextSearchHandler.withRowBlock(block)
                 }
             }
         }
@@ -358,7 +364,7 @@ extension YapDB {
         - parameter persistent: a Bool, defaults to true - meaning that the contents of the view will be stored in YapDatabase between launches.
         - parameter collections: an optional array of collections which is used to white list the collections searched when populating the view.
         */
-        public init(name: String, parent p: YapDB.Fetch, search: String, columnNames cn: [String], handler h: Handler, version: String = "1.0", persistent: Bool = true, collections: [String]? = .None) {
+        public init(name: String, parent p: YapDB.Fetch, search: String, columnNames cn: [String], handler h: Handler, version: String = "1.0", persistent: Bool = true, collections: [String]? = .none) {
             parent = p
             searchName = search
             columnNames = cn
@@ -367,28 +373,28 @@ extension YapDB {
         }
 
         func createDatabaseView() -> YapDatabaseView {
-            return YapDatabaseSearchResultsView(fullTextSearchName: searchName, parentViewName: parent.name, versionTag: version, options: .None)
+            return YapDatabaseSearchResultsView(fullTextSearchName: searchName, parentViewName: parent.name, versionTag: version, options: .none)
         }
 
-        func registerInDatabase(database: YapDatabase, withConnection connection: YapDatabaseConnection? = .None) {
+        func registerInDatabase(_ database: YapDatabase, withConnection connection: YapDatabaseConnection? = .none) {
 
-            if (database.registeredExtension(searchName) as? YapDatabaseFullTextSearch) == .None {
-                let fullTextSearch = YapDatabaseFullTextSearch(columnNames: columnNames, handler: handler.object, versionTag: version)
+            if (database.registeredExtension(searchName) as? YapDatabaseFullTextSearch) == .none {
+                let fullTextSearch = YapDatabaseFullTextSearch(columnNames: columnNames, options: nil, handler: handler.object, versionTag: version)
                 if let connection = connection {
-                    database.registerExtension(fullTextSearch, withName: searchName, connection: connection)
+                    database.register(fullTextSearch, withName: searchName, connection: connection)
                 }
                 else {
-                    database.registerExtension(fullTextSearch, withName: searchName)
+                    database.register(fullTextSearch, withName: searchName)
                 }
             }
 
             if !isRegisteredInDatabase(database) {
                 parent.registerInDatabase(database, withConnection: connection)
                 if let connection = connection {
-                    database.registerExtension(createDatabaseView(), withName: name, connection: connection)
+                    database.register(createDatabaseView(), withName: name, connection: connection)
                 }
                 else {
-                    database.registerExtension(createDatabaseView(), withName: name)
+                    database.register(createDatabaseView(), withName: name)
                 }
             }
         }
@@ -405,20 +411,20 @@ extension YapDB {
     is similar to a full text search extension. It features a handler, which must
     be provided to update a dictionary used to index records.
     */
-    public class SecondaryIndex: BaseExtension, YapDatabaseExtensionRegistrar {
+    open class SecondaryIndex: BaseExtension, YapDatabaseExtensionRegistrar {
 
         public enum Handler {
-            case ByKey(YapDatabaseSecondaryIndexWithKeyBlock)
-            case ByObject(YapDatabaseSecondaryIndexWithObjectBlock)
-            case ByMetadata(YapDatabaseSecondaryIndexWithMetadataBlock)
-            case ByRow(YapDatabaseSecondaryIndexWithRowBlock)
+            case byKey(YapDatabaseSecondaryIndexWithKeyBlock)
+            case byObject(YapDatabaseSecondaryIndexWithObjectBlock)
+            case byMetadata(YapDatabaseSecondaryIndexWithMetadataBlock)
+            case byRow(YapDatabaseSecondaryIndexWithRowBlock)
 
             public var object: YapDatabaseSecondaryIndexHandler {
                 switch self {
-                case let .ByKey(block): return YapDatabaseSecondaryIndexHandler.withKeyBlock(block)
-                case let .ByObject(block): return YapDatabaseSecondaryIndexHandler.withObjectBlock(block)
-                case let .ByMetadata(block): return YapDatabaseSecondaryIndexHandler.withMetadataBlock(block)
-                case let .ByRow(block): return YapDatabaseSecondaryIndexHandler.withRowBlock(block)
+                case let .byKey(block): return YapDatabaseSecondaryIndexHandler.withKeyBlock(block)
+                case let .byObject(block): return YapDatabaseSecondaryIndexHandler.withObjectBlock(block)
+                case let .byMetadata(block): return YapDatabaseSecondaryIndexHandler.withMetadataBlock(block)
+                case let .byRow(block): return YapDatabaseSecondaryIndexHandler.withRowBlock(block)
                 }
             }
         }
@@ -443,19 +449,19 @@ extension YapDB {
         func setup() -> YapDatabaseSecondaryIndexSetup {
             let setup = YapDatabaseSecondaryIndexSetup()
             for (column, indexType) in columnTypes {
-                setup.addColumn(column, withType: indexType)
+                setup.addColumn(column, with: indexType)
             }
             return setup
         }
 
-        public func registerInDatabase(database: YapDatabase, withConnection connection: YapDatabaseConnection?) {
+        open func registerInDatabase(_ database: YapDatabase, withConnection connection: YapDatabaseConnection?) {
             if !isRegisteredInDatabase(database) {
                 let secondaryIndex = YapDatabaseSecondaryIndex(setup: setup(), handler: handler.object, versionTag: version, options: options)
                 if let connection = connection {
-                    database.registerExtension(secondaryIndex, withName: name, connection: connection)
+                    database.register(secondaryIndex, withName: name, connection: connection)
                 }
                 else {
-                    database.registerExtension(secondaryIndex, withName: name)
+                    database.register(secondaryIndex, withName: name)
                 }
             }
         }
@@ -467,9 +473,9 @@ extension YapDB {
     public struct Mappings {
 
         public enum Kind {
-            case Composed(YapDatabaseViewMappings)
-            case Groups([String])
-            case Dynamic((filter: YapDatabaseViewMappingGroupFilter, sorter: YapDatabaseViewMappingGroupSort))
+            case composed(YapDatabaseViewMappings)
+            case groups([String])
+            case dynamic((filter: YapDatabaseViewMappingGroupFilter, sorter: YapDatabaseViewMappingGroupSort))
         }
 
         public static var passThroughFilter: YapDatabaseViewMappingGroupFilter {
@@ -482,25 +488,25 @@ extension YapDB {
 
         let kind: Kind
 
-        public init(filter f: YapDatabaseViewMappingGroupFilter = Mappings.passThroughFilter, sort s: YapDatabaseViewMappingGroupSort = Mappings.caseInsensitiveGroupSort) {
-            kind = .Dynamic((f, s))
+        public init(filter f: @escaping YapDatabaseViewMappingGroupFilter = Mappings.passThroughFilter, sort s: @escaping YapDatabaseViewMappingGroupSort = Mappings.caseInsensitiveGroupSort) {
+            kind = .dynamic((f, s))
         }
 
         public init(groups: [String]) {
-            kind = .Groups(groups)
+            kind = .groups(groups)
         }
 
         public init(composed: YapDatabaseViewMappings) {
-            kind = .Composed(composed)
+            kind = .composed(composed)
         }
 
-        func createMappingsWithViewName(viewName: String) -> YapDatabaseViewMappings {
+        func createMappingsWithViewName(_ viewName: String) -> YapDatabaseViewMappings {
             switch kind {
-            case .Composed(let mappings):
+            case .composed(let mappings):
                 return mappings
-            case .Groups(let groups):
+            case .groups(let groups):
                 return YapDatabaseViewMappings(groups: groups, view: viewName)
-            case .Dynamic(let (filter: filter, sorter: sorter)):
+            case .dynamic(let (filter: filter, sorter: sorter)):
                 return YapDatabaseViewMappings(groupFilterBlock: filter, sortBlock: sorter, view: viewName)
             }
         }
@@ -521,25 +527,25 @@ extension YapDB {
             return fetch.name
         }
 
-        public init(fetch f: Fetch, mappings m: Mappings = Mappings(), block b: MappingsConfigurationBlock? = .None) {
+        public init(fetch f: Fetch, mappings m: Mappings = Mappings(), block b: MappingsConfigurationBlock? = .none) {
             fetch = f
             mappings = m
             block = b
         }
 
         public init(view: YapDB.View) {
-            self.init(fetch: .View(view))
+            self.init(fetch: .view(view))
         }
 
         public init(filter: YapDB.Filter) {
-            self.init(fetch: .Filter(filter))
+            self.init(fetch: .filter(filter))
         }
 
         public init(search: YapDB.SearchResults) {
-            self.init(fetch: .Search(search))
+            self.init(fetch: .search(search))
         }
 
-        public func createMappingsRegisteredInDatabase(database: YapDatabase, withConnection connection: YapDatabaseConnection? = .None) -> YapDatabaseViewMappings {
+        public func createMappingsRegisteredInDatabase(_ database: YapDatabase, withConnection connection: YapDatabaseConnection? = .none) -> YapDatabaseViewMappings {
             let databaseViewMappings = fetch.createViewMappings(mappings, inDatabase: database, withConnection: connection)
             block?(databaseViewMappings)
             return databaseViewMappings
@@ -550,20 +556,20 @@ extension YapDB {
 
 extension YapDB {
 
-    public class Search {
-        public typealias Query = (searchTerm: String) -> String
+    open class Search {
+        public typealias Query = (_ searchTerm: String) -> String
 
         let database: YapDatabase
         let connection: YapDatabaseConnection
         let queues: [(String, YapDatabaseSearchQueue)]
         let query: Query
 
-        public init(db: YapDatabase, views: [YapDB.Fetch], query q: Query) {
+        public init(db: YapDatabase, views: [YapDB.Fetch], query q: @escaping Query) {
             database = db
             connection = db.newConnection()
             let _views = views.filter { fetch in
                 switch fetch {
-                case .Index(_): return false
+                case .index(_): return false
                 default: return true
                 }
             }
@@ -574,18 +580,18 @@ extension YapDB {
             query = q
         }
 
-        public convenience init(db: YapDatabase, view: YapDB.Fetch, query: Query) {
+        public convenience init(db: YapDatabase, view: YapDB.Fetch, query: @escaping Query) {
             self.init(db: db, views: [view], query: query)
         }
 
-        public func usingTerm(term: String) {
+        open func usingTerm(_ term: String) {
             for (_, queue) in queues {
-                queue.enqueueQuery(query(searchTerm: term))
+                queue.enqueueQuery(query(term))
             }
-            connection.asyncReadWriteWithBlock { [queues = self.queues] transaction in
+            connection.asyncReadWrite { [queues = self.queues] transaction in
                 for (name, queue) in queues {
                     if let searchResultsViewTransaction = transaction.ext(name) as? YapDatabaseSearchResultsViewTransaction {
-                        searchResultsViewTransaction.performSearchWithQueue(queue)
+                        searchResultsViewTransaction.performSearch(with: queue)
                     }
                     else {
                         assertionFailure("Error: Attempting search using results view with name: \(name) which isn't a registered database extension.")
diff --git a/Sources/YapDatabaseExtensions.swift b/Sources/YapDatabaseExtensions.swift
index b6cf121..77e5282 100644
--- a/Sources/YapDatabaseExtensions.swift
+++ b/Sources/YapDatabaseExtensions.swift
@@ -22,8 +22,8 @@ public struct YapDB {
     
     - returns: a String representing the path to a database in the given search directory, with the given name/suffix.
     */
-    public static func pathToDatabase(directory: NSSearchPathDirectory, name: String, suffix: String? = .None) -> String {
-        let paths = NSSearchPathForDirectoriesInDomains(directory, .UserDomainMask, true)
+    public static func pathToDatabase(_ directory: FileManager.SearchPathDirectory, name: String, suffix: String? = .none) -> String {
+        let paths = NSSearchPathForDirectoriesInDomains(directory, .userDomainMask, true)
         let directory: String = paths.first ?? NSTemporaryDirectory()
         let filename: String = {
             if let suffix = suffix {
@@ -32,7 +32,7 @@ public struct YapDB {
             return "\(name).sqlite"
         }()
 
-        return (directory as NSString).stringByAppendingPathComponent(filename)
+        return (directory as NSString).appendingPathComponent(filename)
     }
 
     /// Type of closure which can perform operations on newly created/opened database instances.
@@ -73,8 +73,8 @@ public struct YapDB {
     
     - returns: the YapDatabase instance.
     */
-    public static func databaseNamed(name: String, operations: DatabaseOperationsBlock? = .None) -> YapDatabase {
-        let db =  YapDatabase(path: pathToDatabase(.DocumentDirectory, name: name, suffix: .None))
+    public static func databaseNamed(_ name: String, operations: DatabaseOperationsBlock? = .none) -> YapDatabase {
+        let db =  YapDatabase(path: pathToDatabase(.documentDirectory, name: name, suffix: .none))
         operations?(db)
         return db
     }
@@ -105,11 +105,11 @@ public struct YapDB {
     
     - returns: the YapDatabase instance.
     */
-    public static func testDatabase(file: String = #file, test: String = #function, operations: DatabaseOperationsBlock? = .None) -> YapDatabase {
-        let path = pathToDatabase(.CachesDirectory, name: (file as NSString).lastPathComponent, suffix: test.stringByTrimmingCharactersInSet(NSCharacterSet(charactersInString: "()")))
+    public static func testDatabase(_ file: String = #file, test: String = #function, operations: DatabaseOperationsBlock? = .none) -> YapDatabase {
+        let path = pathToDatabase(.cachesDirectory, name: (file as NSString).lastPathComponent, suffix: test.trimmingCharacters(in: CharacterSet(charactersIn: "()")))
         assert(!path.isEmpty, "Path should not be empty.")
         do {
-            try NSFileManager.defaultManager().removeItemAtPath(path)
+            try FileManager.default.removeItem(atPath: path)
         }
         catch { }
 
@@ -193,10 +193,6 @@ Identifier for your String identifiers.
 */
 public typealias Identifier = String
 
-extension Identifier: CustomStringConvertible {
-    public var description: String { return self }
-}
-
 // MARK: - Persistable
 
 /**
@@ -219,7 +215,7 @@ extension Persistable {
     - parameter key: a `String`
     - returns: a `YapDB.Index` value.
     */
-    public static func indexWithKey(key: String) -> YapDB.Index {
+    public static func indexWithKey(_ key: String) -> YapDB.Index {
         return YapDB.Index(collection: collection, key: key)
     }
 
@@ -234,9 +230,9 @@ extension Persistable {
     - returns: an array of `YapDB.Index` values.
     */
     public static func indexesWithKeys<
-        Keys where
-        Keys: SequenceType,
-        Keys.Generator.Element == String>(keys: Keys) -> [YapDB.Index] {
+        Keys>(_ keys: Keys) -> [YapDB.Index] where
+        Keys: Sequence,
+        Keys.Iterator.Element == String {
             return Set(keys).map { YapDB.Index(collection: collection, key: $0) }
     }
 
@@ -256,17 +252,17 @@ extension Persistable {
     - returns: a `YapDB.Index`.
     */
     public var index: YapDB.Index {
-        return self.dynamicType.indexWithKey(key)
+        return type(of: self).indexWithKey(key)
     }
 }
 
 // MARK: Functions
 
-public func keyForPersistable<P: Persistable>(persistable: P) -> String {
+public func keyForPersistable<P: Persistable>(_ persistable: P) -> String {
     return persistable.key
 }
 
-public func indexForPersistable<P: Persistable>(persistable: P) -> YapDB.Index {
+public func indexForPersistable<P: Persistable>(_ persistable: P) -> YapDB.Index {
     return persistable.index
 }
 
@@ -281,7 +277,7 @@ public protocol ReadTransactionType {
     - parameter collection: a String. Not optional.
     - returns: an array of String values.
     */
-    func keysInCollection(collection: String) -> [String]
+    func keysInCollection(_ collection: String) -> [String]
 
     /**
     Read the object at the index.
@@ -289,7 +285,7 @@ public protocol ReadTransactionType {
     - parameter index: a YapDB.Index.
     - returns: an `AnyObject` if an item existing in the database for this index.
     */
-    func readAtIndex(index: YapDB.Index) -> AnyObject?
+    func readAtIndex(_ index: YapDB.Index) -> AnyObject?
 
     /**
     Read the metadata at the index.
@@ -297,7 +293,7 @@ public protocol ReadTransactionType {
     - parameter index: a YapDB.Index.
     - returns: an `AnyObject` if a metadata item existing in the database for this index.
     */
-    func readMetadataAtIndex(index: YapDB.Index) -> AnyObject?
+    func readMetadataAtIndex(_ index: YapDB.Index) -> AnyObject?
 }
 
 /// A facade interface for a write transaction.
@@ -310,7 +306,7 @@ public protocol WriteTransactionType: ReadTransactionType {
     - parameter object: the `AnyObject` which will be written.
     - parameter metadata: an optional `AnyObject` which will be written as metadata.
     */
-    func writeAtIndex(index: YapDB.Index, object: AnyObject, metadata: AnyObject?)
+    func writeAtIndex(_ index: YapDB.Index, object: AnyObject, metadata: AnyObject?)
 
     /**
     Remove the sequence object from the database at the indexes (if it exists), including metadata
@@ -318,9 +314,9 @@ public protocol WriteTransactionType: ReadTransactionType {
     - parameter indexes: the `[YapDB.Index]` to remove.
     */
     func removeAtIndexes<
-        Indexes where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index>(indexes: Indexes)
+        Indexes>(_ indexes: Indexes) where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index
 }
 
 /// A facade interface for a database connection.
@@ -339,7 +335,7 @@ public protocol ConnectionType {
     - parameter block: a closure which receives YapDatabaseReadTransaction and returns T
     - returns: An instance of T
     */
-    func read<T>(block: ReadTransaction -> T) -> T
+    func read<T>(_ block: @escaping (ReadTransaction) -> T) -> T
 
     /**
     Synchronously writes to the database on the connection. The closure receives
@@ -352,7 +348,7 @@ public protocol ConnectionType {
     - parameter block: a closure which receives YapDatabaseReadWriteTransaction and returns T
     - returns: An instance of T
     */
-    func write<T>(block: WriteTransaction -> T) -> T
+    func write<T>(_ block: @escaping (WriteTransaction) -> T) -> T
 
     /**
     Asynchronously reads from the database on the connection. The closure receives
@@ -368,7 +364,7 @@ public protocol ConnectionType {
     - parameter queue: a dispatch_queue_t, defaults to main queue, can be ommitted in most cases.
     - parameter completion: a closure which receives T and returns Void.
     */
-    func asyncRead<T>(block: ReadTransaction -> T, queue: dispatch_queue_t, completion: (T) -> Void)
+    func asyncRead<T>(_ block: @escaping (ReadTransaction) -> T, queue: DispatchQueue, completion: @escaping (T) -> Void)
 
     /**
     Asynchronously writes to the database on the connection. The closure receives
@@ -384,7 +380,7 @@ public protocol ConnectionType {
     - parameter queue: a dispatch_queue_t, defaults to main queue, can be ommitted in most cases.
     - parameter completion: a closure which receives T and returns Void.
     */
-    func asyncWrite<T>(block: WriteTransaction -> T, queue: dispatch_queue_t, completion: (T -> Void)?)
+    func asyncWrite<T>(_ block: @escaping (WriteTransaction) -> T, queue: DispatchQueue, completion: ((T) -> Void)?)
 
     /**
     Execute a read/write block inside a `NSOperation`. The block argument receives a
@@ -400,7 +396,7 @@ public protocol ConnectionType {
     - parameter block: a closure of type (YapDatabaseReadWriteTransaction) -> Void
     - returns: an `NSOperation`.
     */
-    func writeBlockOperation(block: WriteTransaction -> Void) -> NSOperation
+    func writeBlockOperation(_ block: @escaping (WriteTransaction) -> Void) -> Operation
 }
 
 /// A facade interface for a database.
@@ -410,9 +406,9 @@ public protocol DatabaseType {
 }
 
 internal enum Handle<D: DatabaseType> {
-    case Transaction(D.Connection.ReadTransaction)
-    case Connection(D.Connection)
-    case Database(D)
+    case transaction(D.Connection.ReadTransaction)
+    case connection(D.Connection)
+    case database(D)
 }
 
 // MARK: - YapDatabaseReadTransaction
@@ -425,8 +421,8 @@ extension YapDatabaseReadTransaction: ReadTransactionType {
     - parameter collection: a String.
     - returns: an array of String values.
     */
-    public func keysInCollection(collection: String) -> [String] {
-        return allKeysInCollection(collection)
+    public func keysInCollection(_ collection: String) -> [String] {
+        return allKeys(inCollection: collection)
     }
 
     /**
@@ -435,8 +431,8 @@ extension YapDatabaseReadTransaction: ReadTransactionType {
     - parameter index: The YapDB.Index value.
     - returns: An optional AnyObject.
     */
-    public func readAtIndex(index: YapDB.Index) -> AnyObject? {
-        return objectForKey(index.key, inCollection: index.collection)
+    public func readAtIndex(_ index: YapDB.Index) -> AnyObject? {
+        return object(forKey: index.key, inCollection: index.collection) as AnyObject?
     }
 
     /**
@@ -445,8 +441,8 @@ extension YapDatabaseReadTransaction: ReadTransactionType {
     - parameter index: The YapDB.Index value.
     - returns: An optional AnyObject.
     */
-    public func readMetadataAtIndex(index: YapDB.Index) -> AnyObject? {
-        return metadataForKey(index.key, inCollection: index.collection)
+    public func readMetadataAtIndex(_ index: YapDB.Index) -> AnyObject? {
+        return metadata(forKey: index.key, inCollection: index.collection) as AnyObject?
     }
 }
 
@@ -454,7 +450,7 @@ extension YapDatabaseReadTransaction: ReadTransactionType {
 
 extension YapDatabaseReadWriteTransaction: WriteTransactionType {
 
-    public func writeAtIndex(index: YapDB.Index, object: AnyObject, metadata: AnyObject? = .None) {
+    public func writeAtIndex(_ index: YapDB.Index, object: AnyObject, metadata: AnyObject? = .none) {
         if let metadata: AnyObject = metadata {
             setObject(object, forKey: index.key, inCollection: index.collection, withMetadata: metadata)
         }
@@ -463,14 +459,14 @@ extension YapDatabaseReadWriteTransaction: WriteTransactionType {
         }
     }
 
-    func removeAtIndex(index: YapDB.Index) {
-        removeObjectForKey(index.key, inCollection: index.collection)
+    func removeAtIndex(_ index: YapDB.Index) {
+        removeObject(forKey: index.key, inCollection: index.collection)
     }
 
     public func removeAtIndexes<
-        Indexes where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index>(indexes: Indexes) {
+        Indexes>(_ indexes: Indexes) where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index {
             indexes.forEach(removeAtIndex)
     }
 }
@@ -488,9 +484,9 @@ extension YapDatabaseConnection: ConnectionType {
     - parameter block: a closure which receives YapDatabaseReadTransaction and returns T
     - returns: An instance of T
     */
-    public func read<T>(block: YapDatabaseReadTransaction -> T) -> T {
-        var result: T! = .None
-        readWithBlock { result = block($0) }
+    public func read<T>(_ block: @escaping (YapDatabaseReadTransaction) -> T) -> T {
+        var result: T! = .none
+        self.read { result = block($0) }
         return result
     }
 
@@ -505,9 +501,9 @@ extension YapDatabaseConnection: ConnectionType {
     - parameter block: a closure which receives YapDatabaseReadWriteTransaction and returns T
     - returns: An instance of T
     */
-    public func write<T>(block: YapDatabaseReadWriteTransaction -> T) -> T {
-        var result: T! = .None
-        readWriteWithBlock { result = block($0) }
+    public func write<T>(_ block: @escaping (YapDatabaseReadWriteTransaction) -> T) -> T {
+        var result: T! = .none
+        readWrite { result = block($0) }
         return result
     }
 
@@ -525,9 +521,9 @@ extension YapDatabaseConnection: ConnectionType {
     - parameter queue: a dispatch_queue_t, defaults to main queue, can be ommitted in most cases.
     - parameter completion: a closure which receives T and returns Void.
     */
-    public func asyncRead<T>(block: YapDatabaseReadTransaction -> T, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: (T) -> Void) {
-        var result: T! = .None
-        asyncReadWithBlock({ result = block($0) }, completionQueue: queue) { completion(result) }
+    public func asyncRead<T>(_ block: @escaping (YapDatabaseReadTransaction) -> T, queue: DispatchQueue = DispatchQueue.main, completion: @escaping (T) -> Void) {
+        var result: T! = .none
+        self.asyncRead({ result = block($0) }, completionQueue: queue) { completion(result) }
     }
 
     /**
@@ -544,9 +540,9 @@ extension YapDatabaseConnection: ConnectionType {
     - parameter queue: a dispatch_queue_t, defaults to main queue, can be ommitted in most cases.
     - parameter completion: a closure which receives T and returns Void.
     */
-    public func asyncWrite<T>(block: YapDatabaseReadWriteTransaction -> T, queue: dispatch_queue_t = dispatch_get_main_queue(), completion: (T -> Void)?) {
-        var result: T! = .None
-        asyncReadWriteWithBlock({ result = block($0) }, completionQueue: queue) { completion?(result) }
+    public func asyncWrite<T>(_ block: @escaping (YapDatabaseReadWriteTransaction) -> T, queue: DispatchQueue = DispatchQueue.main, completion: ((T) -> Void)?) {
+        var result: T! = .none
+        asyncReadWrite({ result = block($0) }, completionQueue: queue) { completion?(result) }
     }
 
     /**
@@ -563,8 +559,8 @@ extension YapDatabaseConnection: ConnectionType {
     - parameter block: a closure of type (YapDatabaseReadWriteTransaction) -> Void
     - returns: an `NSOperation`.
     */
-    public func writeBlockOperation(block: (YapDatabaseReadWriteTransaction) -> Void) -> NSOperation {
-        return NSBlockOperation { self.readWriteWithBlock(block) }
+    public func writeBlockOperation(_ block: @escaping (YapDatabaseReadWriteTransaction) -> Void) -> Operation {
+        return BlockOperation { self.readWrite(block) }
     }
 }
 
@@ -607,7 +603,7 @@ extension YapDB.Index: ValueCoding {
 
 // MARK: Coders
 
-public final class YapDBIndexCoder: NSObject, NSCoding, CodingType {
+public final class YapDBIndexCoder: NSObject, NSCoding, CodingProtocol {
     public let value: YapDB.Index
 
     public init(_ v: YapDB.Index) {
@@ -615,33 +611,33 @@ public final class YapDBIndexCoder: NSObject, NSCoding, CodingType {
     }
 
     public required init(coder aDecoder: NSCoder) {
-        let collection = aDecoder.decodeObjectForKey("collection") as! String
-        let key = aDecoder.decodeObjectForKey("key") as! String
+        let collection = aDecoder.decodeObject(forKey: "collection") as! String
+        let key = aDecoder.decodeObject(forKey: "key") as! String
         value = YapDB.Index(collection: collection, key: key)
     }
 
-    public func encodeWithCoder(aCoder: NSCoder) {
-        aCoder.encodeObject(value.collection, forKey: "collection")
-        aCoder.encodeObject(value.key, forKey: "key")
+    public func encode(with aCoder: NSCoder) {
+        aCoder.encode(value.collection, forKey: "collection")
+        aCoder.encode(value.key, forKey: "key")
     }
 }
 
 // MARK: - Deprecations
 
-@available(*, unavailable, renamed="Persistable")
+@available(*, unavailable, renamed: "Persistable")
 public typealias MetadataPersistable = Persistable
 
-@available(*, unavailable, renamed="Persistable")
+@available(*, unavailable, renamed: "Persistable")
 public typealias ObjectMetadataPersistable = Persistable
 
-@available(*, unavailable, renamed="Persistable")
+@available(*, unavailable, renamed: "Persistable")
 public typealias ValueMetadataPersistable = Persistable
 
-@available(*, unavailable, renamed="ValueCoding")
+@available(*, unavailable, renamed: "ValueCoding")
 public typealias Saveable = ValueCoding
 
-@available(*, unavailable, renamed="CodingType")
-public typealias Archiver = CodingType
-
-
+@available(*, unavailable, renamed: "CodingProtocol")
+public typealias CodingType = CodingProtocol
 
+@available(*, unavailable, renamed: "CodingProtocol")
+public typealias Archiver = CodingProtocol
diff --git a/Supporting Files/Version.xcconfig b/Supporting Files/Version.xcconfig
index cd3083e..bf8fe70 100644
--- a/Supporting Files/Version.xcconfig	
+++ b/Supporting Files/Version.xcconfig	
@@ -1 +1 @@
-YAP_DATABASE_EXTENSIONS_VERSION = 2.6.0
+YAP_DATABASE_EXTENSIONS_VERSION = 3.0.0
diff --git a/Supporting Files/YapDatabaseExtensions.xcconfig b/Supporting Files/YapDatabaseExtensions.xcconfig
index bcbbfc1..3c1ebd9 100644
--- a/Supporting Files/YapDatabaseExtensions.xcconfig	
+++ b/Supporting Files/YapDatabaseExtensions.xcconfig	
@@ -11,8 +11,8 @@ INFOPLIST_FILE_framework = $(SRCROOT)/Supporting Files/Info.plist
 INFOPLIST_FILE_xctest = $(SRCROOT)/Tests/Info.plist
 INFOPLIST_FILE = $(INFOPLIST_FILE_$(WRAPPER_EXTENSION))
 
-PRODUCT_BUNDLE_IDENTIFIER_framework = me.danthorpe.YapDatabaseExtensions
-PRODUCT_BUNDLE_IDENTIFIER_xctest = me.danthorpe.YapDatabaseExtensionsTests
+PRODUCT_BUNDLE_IDENTIFIER_framework = com.roepcke.YapDatabaseExtensions
+PRODUCT_BUNDLE_IDENTIFIER_xctest = com.roepcke.YapDatabaseExtensionsTests
 PRODUCT_BUNDLE_IDENTIFIER = $(PRODUCT_BUNDLE_IDENTIFIER_$(WRAPPER_EXTENSION))
 
 PRODUCT_NAME_framework = YapDatabaseExtensions
@@ -23,7 +23,7 @@ APPLICATION_EXTENSION_API_ONLY_framework = YES
 APPLICATION_EXTENSION_API_ONLY_xctest = NO
 APPLICATION_EXTENSION_API_ONLY = $(APPLICATION_EXTENSION_API_ONLY_$(WRAPPER_EXTENSION))
 
-SWIFT_VERSION = 2.3
+SWIFT_VERSION = 3.0
 
 // Build Settings
 SUPPORTED_PLATFORMS = macosx iphoneos appletvos watchos appletvsimulator iphonesimulator watchsimulator
diff --git a/Tests/Models.swift b/Tests/Models.swift
index 22a2efa..f447a0a 100644
--- a/Tests/Models.swift
+++ b/Tests/Models.swift
@@ -12,8 +12,8 @@ import YapDatabase
 import YapDatabaseExtensions
 
 public enum Barcode: Equatable {
-    case UPCA(Int, Int, Int, Int)
-    case QRCode(String)
+    case upca(Int, Int, Int, Int)
+    case qrCode(String)
 }
 
 public struct Product: Identifiable, Equatable {
@@ -61,13 +61,13 @@ public class NamedEntity: NSObject, NSCoding {
     }
 
     public required init?(coder aDecoder: NSCoder) {
-        identifier = aDecoder.decodeObjectForKey("identifier") as! Identifier
-        name = aDecoder.decodeObjectForKey("name") as! String
+        identifier = aDecoder.decodeObject(forKey: "identifier") as! Identifier
+        name = aDecoder.decodeObject(forKey: "name") as! String
     }
 
-    public func encodeWithCoder(aCoder: NSCoder) {
-        aCoder.encodeObject(identifier, forKey: "identifier")
-        aCoder.encodeObject(name, forKey: "name")
+    public func encode(with aCoder: NSCoder) {
+        aCoder.encode(identifier, forKey: "identifier")
+        aCoder.encode(name, forKey: "name")
     }
 }
 
@@ -86,9 +86,9 @@ public class Manager: NamedEntity {
 
 public func == (a: Barcode, b: Barcode) -> Bool {
     switch (a, b) {
-    case let (.UPCA(aNS, aM, aP, aC), .UPCA(bNS, bM, bP, bC)):
+    case let (.upca(aNS, aM, aP, aC), .upca(bNS, bM, bP, bC)):
         return (aNS == bNS) && (aM == bM) && (aP == bP) && (aC == bC)
-    case let (.QRCode(aCode), .QRCode(bCode)):
+    case let (.qrCode(aCode), .qrCode(bCode)):
         return aCode == bCode
     default:
         return false
@@ -164,9 +164,9 @@ extension Barcode: Persistable {
 
     public var identifier: Int {
         switch self {
-        case let .UPCA(numberSystem, manufacturer, product, check):
+        case let .upca(numberSystem, manufacturer, product, check):
             return "\(numberSystem).\(manufacturer).\(product).\(check)".hashValue
-        case let .QRCode(code):
+        case let .qrCode(code):
             return code.hashValue
         }
     }
@@ -220,12 +220,12 @@ extension Manager: Persistable {
 extension Barcode: ValueCoding {
     public typealias Coder = BarcodeCoder
 
-    enum Kind: Int { case UPCA = 1, QRCode }
+    enum Kind: Int { case upca = 1, qrCode }
 
     var kind: Kind {
         switch self {
-        case UPCA(_): return Kind.UPCA
-        case QRCode(_): return Kind.QRCode
+        case .upca(_): return Kind.upca
+        case .qrCode(_): return Kind.qrCode
         }
     }
 }
@@ -253,7 +253,7 @@ extension Manager.Metadata: ValueCoding {
 
 // MARK: - Coders
 
-public class BarcodeCoder: NSObject, NSCoding, CodingType {
+public class BarcodeCoder: NSObject, NSCoding, CodingProtocol {
     public let value: Barcode
 
     public required init(_ v: Barcode) {
@@ -261,17 +261,17 @@ public class BarcodeCoder: NSObject, NSCoding, CodingType {
     }
 
     public required init?(coder aDecoder: NSCoder) {
-        if let kind = Barcode.Kind(rawValue: aDecoder.decodeIntegerForKey("kind")) {
+        if let kind = Barcode.Kind(rawValue: aDecoder.decodeInteger(forKey: "kind")) {
             switch kind {
-            case .UPCA:
-                let numberSystem = aDecoder.decodeIntegerForKey("numberSystem")
-                let manufacturer = aDecoder.decodeIntegerForKey("manufacturer")
-                let product = aDecoder.decodeIntegerForKey("product")
-                let check = aDecoder.decodeIntegerForKey("check")
-                value = .UPCA(numberSystem, manufacturer, product, check)
-            case .QRCode:
-                let code = aDecoder.decodeObjectForKey("code") as! String
-                value = .QRCode(code)
+            case .upca:
+                let numberSystem = aDecoder.decodeInteger(forKey: "numberSystem")
+                let manufacturer = aDecoder.decodeInteger(forKey: "manufacturer")
+                let product = aDecoder.decodeInteger(forKey: "product")
+                let check = aDecoder.decodeInteger(forKey: "check")
+                value = .upca(numberSystem, manufacturer, product, check)
+            case .qrCode:
+                let code = aDecoder.decodeObject(forKey: "code") as! String
+                value = .qrCode(code)
             }
         }
         else {
@@ -279,21 +279,21 @@ public class BarcodeCoder: NSObject, NSCoding, CodingType {
         }
     }
 
-    public func encodeWithCoder(aCoder: NSCoder) {
-        aCoder.encodeInteger(value.kind.rawValue, forKey: "kind")
+    public func encode(with aCoder: NSCoder) {
+        aCoder.encode(value.kind.rawValue, forKey: "kind")
         switch value {
-        case let .UPCA(numberSystem, manufacturer, product, check):
-            aCoder.encodeInteger(numberSystem, forKey: "numberSystem")
-            aCoder.encodeInteger(manufacturer, forKey: "manufacturer")
-            aCoder.encodeInteger(product, forKey: "product")
-            aCoder.encodeInteger(check, forKey: "check")
-        case let .QRCode(code):
-            aCoder.encodeObject(code, forKey: "code")
+        case let .upca(numberSystem, manufacturer, product, check):
+            aCoder.encode(numberSystem, forKey: "numberSystem")
+            aCoder.encode(manufacturer, forKey: "manufacturer")
+            aCoder.encode(product, forKey: "product")
+            aCoder.encode(check, forKey: "check")
+        case let .qrCode(code):
+            aCoder.encode(code, forKey: "code")
         }
     }
 }
 
-public class ProductCategoryCoder: NSObject, NSCoding, CodingType {
+public class ProductCategoryCoder: NSObject, NSCoding, CodingProtocol {
     public let value: Product.Category
 
     public required init(_ v: Product.Category) {
@@ -301,18 +301,18 @@ public class ProductCategoryCoder: NSObject, NSCoding, CodingType {
     }
 
     public required init?(coder aDecoder: NSCoder) {
-        let identifier = aDecoder.decodeIntegerForKey("identifier")
-        let name = aDecoder.decodeObjectForKey("name") as? String
+        let identifier = aDecoder.decodeInteger(forKey: "identifier")
+        let name = aDecoder.decodeObject(forKey: "name") as? String
         value = Product.Category(identifier: identifier, name: name!)
     }
 
-    public func encodeWithCoder(aCoder: NSCoder) {
-        aCoder.encodeInteger(value.identifier, forKey: "identifier")
-        aCoder.encodeObject(value.name, forKey: "name")
+    public func encode(with aCoder: NSCoder) {
+        aCoder.encode(value.identifier, forKey: "identifier")
+        aCoder.encode(value.name, forKey: "name")
     }
 }
 
-public class ProductMetadataCoder: NSObject, NSCoding, CodingType {
+public class ProductMetadataCoder: NSObject, NSCoding, CodingProtocol {
     public let value: Product.Metadata
 
     public required init(_ v: Product.Metadata) {
@@ -320,16 +320,16 @@ public class ProductMetadataCoder: NSObject, NSCoding, CodingType {
     }
 
     public required init?(coder aDecoder: NSCoder) {
-        let categoryIdentifier = aDecoder.decodeIntegerForKey("categoryIdentifier")
+        let categoryIdentifier = aDecoder.decodeInteger(forKey: "categoryIdentifier")
         value = Product.Metadata(categoryIdentifier: categoryIdentifier)
     }
 
-    public func encodeWithCoder(aCoder: NSCoder) {
-        aCoder.encodeInteger(value.categoryIdentifier, forKey: "categoryIdentifier")
+    public func encode(with aCoder: NSCoder) {
+        aCoder.encode(value.categoryIdentifier, forKey: "categoryIdentifier")
     }
 }
 
-public class ProductCoder: NSObject, NSCoding, CodingType {
+public class ProductCoder: NSObject, NSCoding, CodingProtocol {
     public let value: Product
 
     public required init(_ v: Product) {
@@ -337,20 +337,20 @@ public class ProductCoder: NSObject, NSCoding, CodingType {
     }
 
     public required init?(coder aDecoder: NSCoder) {
-        let identifier = aDecoder.decodeObjectForKey("identifier") as! String
-        let name = aDecoder.decodeObjectForKey("name") as! String
-        let barcode = Barcode.decode(aDecoder.decodeObjectForKey("barcode"))
+        let identifier = aDecoder.decodeObject(forKey: "identifier") as! String
+        let name = aDecoder.decodeObject(forKey: "name") as! String
+        let barcode = Barcode.decode(aDecoder.decodeObject(forKey: "barcode"))
         value = Product(identifier: identifier, name: name, barcode: barcode!)
     }
 
-    public func encodeWithCoder(aCoder: NSCoder) {
-        aCoder.encodeObject(value.identifier, forKey: "identifier")
-        aCoder.encodeObject(value.name, forKey: "name")
-        aCoder.encodeObject(value.barcode.encoded, forKey: "barcode")
+    public func encode(with aCoder: NSCoder) {
+        aCoder.encode(value.identifier, forKey: "identifier")
+        aCoder.encode(value.name, forKey: "name")
+        aCoder.encode(value.barcode.encoded, forKey: "barcode")
     }
 }
 
-public class InventoryCoder: NSObject, NSCoding, CodingType {
+public class InventoryCoder: NSObject, NSCoding, CodingProtocol {
     public let value: Inventory
 
     public required init(_ v: Inventory) {
@@ -358,17 +358,17 @@ public class InventoryCoder: NSObject, NSCoding, CodingType {
     }
 
     public required init?(coder aDecoder: NSCoder) {
-        let product = Product.decode(aDecoder.decodeObjectForKey("product"))
+        let product = Product.decode(aDecoder.decodeObject(forKey: "product"))
         value = Inventory(product: product!)
     }
 
-    public func encodeWithCoder(aCoder: NSCoder) {
-        aCoder.encodeObject(value.product.encoded, forKey: "product")
+    public func encode(with aCoder: NSCoder) {
+        aCoder.encode(value.product.encoded, forKey: "product")
     }
 }
 
 
-public class ManagerMetadataCoder: NSObject, NSCoding, CodingType {
+public class ManagerMetadataCoder: NSObject, NSCoding, CodingProtocol {
     public let value: Manager.Metadata
 
     public required init(_ v: Manager.Metadata) {
@@ -376,12 +376,12 @@ public class ManagerMetadataCoder: NSObject, NSCoding, CodingType {
     }
 
     public required init?(coder aDecoder: NSCoder) {
-        let numberOfDirectReports = aDecoder.decodeIntegerForKey("numberOfDirectReports")
+        let numberOfDirectReports = aDecoder.decodeInteger(forKey: "numberOfDirectReports")
         value = Manager.Metadata(numberOfDirectReports: numberOfDirectReports)
     }
 
-    public func encodeWithCoder(aCoder: NSCoder) {
-        aCoder.encodeInteger(value.numberOfDirectReports, forKey: "numberOfDirectReports")
+    public func encode(with aCoder: NSCoder) {
+        aCoder.encode(value.numberOfDirectReports, forKey: "numberOfDirectReports")
     }
 }
 
@@ -389,7 +389,7 @@ public class ManagerMetadataCoder: NSObject, NSCoding, CodingType {
 
 public func products() -> YapDB.Fetch {
 
-    let grouping: YapDB.View.Grouping = .ByMetadata({ (_, collection, key, metadata) -> String! in
+    let grouping: YapDB.View.Grouping = .byMetadata({ (_, collection, key, metadata) -> String! in
         if collection == Product.collection {
             if let metadata = Product.Metadata.decode(metadata) {
                 return "category: \(metadata.categoryIdentifier)"
@@ -398,13 +398,13 @@ public func products() -> YapDB.Fetch {
         return nil
     })
 
-    let sorting: YapDB.View.Sorting = .ByObject({ (_, group, collection1, key1, object1, collection2, key2, object2) -> NSComparisonResult in
+    let sorting: YapDB.View.Sorting = .byObject({ (_, group, collection1, key1, object1, collection2, key2, object2) -> ComparisonResult in
         if let product1 = Product.decode(object1) {
             if let product2 = Product.decode(object2) {
                 return product1.name.caseInsensitiveCompare(product2.name)
             }
         }
-        return .OrderedSame
+        return .orderedSame
     })
 
     let view = YapDB.View(
@@ -413,7 +413,7 @@ public func products() -> YapDB.Fetch {
         sorting: sorting,
         collections: [Product.collection])
 
-    return .View(view)
+    return .view(view)
 }
 
 
diff --git a/Tests/ObjectWithNoMetadataTests.swift b/Tests/ObjectWithNoMetadataTests.swift
index 5c125d6..21e6963 100644
--- a/Tests/ObjectWithNoMetadataTests.swift
+++ b/Tests/ObjectWithNoMetadataTests.swift
@@ -29,8 +29,8 @@ class ObjectWithNoMetadataTests: XCTestCase {
 
     var reader: Read<TypeUnderTest, TestableDatabase>!
 
-    var dispatchQueue: dispatch_queue_t!
-    var operationQueue: NSOperationQueue!
+    var dispatchQueue: DispatchQueue!
+    var operationQueue: OperationQueue!
 
     override func setUp() {
         super.setUp()
@@ -50,8 +50,8 @@ class ObjectWithNoMetadataTests: XCTestCase {
         connection.writeTransaction = writeTransaction
         database.connection = connection
 
-        dispatchQueue = dispatch_get_global_queue(QOS_CLASS_DEFAULT, 0)
-        operationQueue = NSOperationQueue()
+        dispatchQueue = DispatchQueue.global(qos: .default)
+        operationQueue = OperationQueue()
     }
 
     override func tearDown() {
@@ -90,7 +90,7 @@ class ObjectWithNoMetadataTests: XCTestCase {
         readTransaction.keys = keys
     }
 
-    func checkTransactionDidWriteItem(result: TypeUnderTest) {
+    func checkTransactionDidWriteItem(_ result: TypeUnderTest) {
         XCTAssertEqual(result.identifier, item.identifier)
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
         XCTAssertEqual(writeTransaction.didWriteAtIndexes[0].0, index)
@@ -98,15 +98,15 @@ class ObjectWithNoMetadataTests: XCTestCase {
         XCTAssertNil(writeTransaction.didWriteAtIndexes[0].2)
     }
 
-    func checkTransactionDidWriteItems(result: [TypeUnderTest]) {
+    func checkTransactionDidWriteItems(_ result: [TypeUnderTest]) {
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
-        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sort(), indexes.map { $0.key }.sort())
+        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sorted(), indexes.map { $0.key }.sorted())
         XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.2 }.count, items.count)
         XCTAssertFalse(result.isEmpty)
         XCTAssertEqual(Set(result), Set(items))
     }
 
-    func checkTransactionDidReadItem(result: TypeUnderTest?) -> Bool {
+    func checkTransactionDidReadItem(_ result: TypeUnderTest?) -> Bool {
         guard let result = result else {
             return false
         }
@@ -115,12 +115,12 @@ class ObjectWithNoMetadataTests: XCTestCase {
         return true
     }
 
-    func checkTransactionDidReadItems(result: [TypeUnderTest]) -> Bool {
-        if result.isEmpty {
+    func checkTransactionDidReadItems(_ result: [TypeUnderTest?]) -> Bool {
+        if result.flatMap({$0}).isEmpty {
             return false
         }
         XCTAssertEqual(Set(readTransaction.didReadAtIndexes), Set(indexes))
-        XCTAssertEqual(result.count, items.count)
+        XCTAssertEqual(result.flatMap({$0}).count, items.count)
         return true
     }
 
@@ -287,24 +287,24 @@ class Functional_Write_ObjectWithNoMetadataTests: ObjectWithNoMetadataTests {
 
     func test__connection__async_write_item() {
         var result: TypeUnderTest!
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         connection.asyncWrite(item) { tmp in
             result = tmp
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItem(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection__async_write_items() {
         var result: [TypeUnderTest] = []
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         connection.asyncWrite(items) { received in
             result = received
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItems(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
@@ -339,23 +339,23 @@ class Functional_Remove_ObjectWithNoMetadataTests: ObjectWithNoMetadataTests {
     }
 
     func test__connection_async_remove_item() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingSingle()
         connection.asyncRemove(item) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItem()
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection_async_remove_items() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingMultiple()
         connection.asyncRemove(items) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItems()
         XCTAssertTrue(connection.didAsyncWrite)
     }
@@ -554,8 +554,8 @@ class Persistable_Read_ObjectWithNoMetadataTests: ObjectWithNoMetadataTests {
         reader = Read(readTransaction)
         let (items, missing) = reader.filterExisting(keys)
         XCTAssertEqual(readTransaction.didReadAtIndexes.first!, indexes.first!)
-        XCTAssertEqual(items.map { $0.identifier }, items.prefixUpTo(1).map { $0.identifier })
-        XCTAssertEqual(missing, Array(keys.suffixFrom(1)))
+        XCTAssertEqual(items.map { $0.identifier }, items.prefix(upTo: 1).map { $0.identifier })
+        XCTAssertEqual(missing, Array(keys.suffix(from: 1)))
     }
 
     // Reading - With Connection
@@ -633,8 +633,8 @@ class Persistable_Read_ObjectWithNoMetadataTests: ObjectWithNoMetadataTests {
         let (items, missing) = reader.filterExisting(keys)
         XCTAssertTrue(connection.didRead)
         XCTAssertEqual(readTransaction.didReadAtIndexes.first!, indexes.first!)
-        XCTAssertEqual(items.map { $0.identifier }, items.prefixUpTo(1).map { $0.identifier })
-        XCTAssertEqual(missing, Array(keys.suffixFrom(1)))
+        XCTAssertEqual(items.map { $0.identifier }, items.prefix(upTo: 1).map { $0.identifier })
+        XCTAssertEqual(missing, Array(keys.suffix(from: 1)))
     }
 
 }
@@ -651,20 +651,20 @@ class Persistable_Write_ObjectWithNoMetadataTests: ObjectWithNoMetadataTests {
     }
 
     func test__item_persistable__write_async_using_connection() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         var result: TypeUnderTest! = nil
 
         item.asyncWrite(connection) { tmp in
             result = tmp
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItem(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__item_persistable__write_using_opertion() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
 
         let operation = item.writeOperation(connection)
         operation.completionBlock = {
@@ -672,7 +672,7 @@ class Persistable_Write_ObjectWithNoMetadataTests: ObjectWithNoMetadataTests {
         }
 
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
         XCTAssertEqual(writeTransaction.didWriteAtIndexes[0].0, index)
         XCTAssertEqual(writeTransaction.didWriteAtIndexes[0].1.identifier, item.identifier)
@@ -690,20 +690,20 @@ class Persistable_Write_ObjectWithNoMetadataTests: ObjectWithNoMetadataTests {
     }
 
     func test__items_persistable__write_async_using_connection() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         var result: [TypeUnderTest] = []
 
         items.asyncWrite(connection) { tmp in
             result = tmp
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItems(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__items_persistable__write_using_opertion() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
 
         let operation = items.writeOperation(connection)
         operation.completionBlock = {
@@ -711,9 +711,9 @@ class Persistable_Write_ObjectWithNoMetadataTests: ObjectWithNoMetadataTests {
         }
 
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
-        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sort(), indexes.map { $0.key }.sort())
+        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sorted(), indexes.map { $0.key }.sorted())
         XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.2 }.count, items.count)
         XCTAssertTrue(connection.didWrite)
     }
@@ -735,25 +735,25 @@ class Persistable_Remove_ObjectWithNoMetadataTests: ObjectWithNoMetadataTests {
     }
 
     func test__connection_async_remove_item() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingSingle()
         item.asyncRemove(connection) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItem()
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection_operation_remove_item() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingSingle()
         let operation = item.removeOperation(connection)
         operation.completionBlock = {
             expectation.fulfill()
         }
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItem()
         XCTAssertTrue(connection.didWrite)
     }
@@ -773,25 +773,25 @@ class Persistable_Remove_ObjectWithNoMetadataTests: ObjectWithNoMetadataTests {
     }
 
     func test__connection_async_remove_items() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingMultiple()
         items.asyncRemove(connection) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItems()
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection_operation_remove_items() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingMultiple()
         let operation = items.removeOperation(connection)
         operation.completionBlock = {
             expectation.fulfill()
         }
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItems()
         XCTAssertTrue(connection.didWrite)
     }
diff --git a/Tests/ObjectWithObjectMetadataTests.swift b/Tests/ObjectWithObjectMetadataTests.swift
index ea690a2..21bd9f6 100644
--- a/Tests/ObjectWithObjectMetadataTests.swift
+++ b/Tests/ObjectWithObjectMetadataTests.swift
@@ -32,8 +32,8 @@ class ObjectWithObjectMetadataTests: XCTestCase {
 
     var reader: Read<TypeUnderTest, TestableDatabase>!
 
-    var dispatchQueue: dispatch_queue_t!
-    var operationQueue: NSOperationQueue!
+    var dispatchQueue: DispatchQueue!
+    var operationQueue: OperationQueue!
 
     override func setUp() {
         super.setUp()
@@ -53,8 +53,8 @@ class ObjectWithObjectMetadataTests: XCTestCase {
         connection.writeTransaction = writeTransaction
         database.connection = connection
 
-        dispatchQueue = dispatch_get_global_queue(QOS_CLASS_DEFAULT, 0)
-        operationQueue = NSOperationQueue()
+        dispatchQueue = DispatchQueue.global(qos: .default)
+        operationQueue = OperationQueue()
     }
 
     override func tearDown() {
@@ -86,12 +86,12 @@ class ObjectWithObjectMetadataTests: XCTestCase {
             TypeUnderTest(id: "beatle-4", name: "Ringo")
         ]
         metadatas = [metadata]
-        items.suffixFrom(1).forEach { _ in metadatas.append(NSDate()) }
+        items.suffix(from: 1).forEach { _ in metadatas.append(NSDate()) }
     }
 
     func configureForReadingSingle() {
         readTransaction.object = item
-        readTransaction.metadata = metadata
+        readTransaction.metadata = metadata as AnyObject?
     }
 
     func configureForReadingMultiple() {
@@ -100,7 +100,7 @@ class ObjectWithObjectMetadataTests: XCTestCase {
         readTransaction.keys = keys
     }
 
-    func checkTransactionDidWriteItem(result: YapItem<TypeUnderTest, MetadataTypeUnderTest>) {
+    func checkTransactionDidWriteItem(_ result: YapItem<TypeUnderTest, MetadataTypeUnderTest>) {
         XCTAssertEqual(result.value.identifier, item.identifier)
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
         XCTAssertEqual(writeTransaction.didWriteAtIndexes[0].0, index)
@@ -108,15 +108,15 @@ class ObjectWithObjectMetadataTests: XCTestCase {
         XCTAssertEqual(writeTransaction.didWriteAtIndexes[0].2 as? NSDate, metadata)
     }
 
-    func checkTransactionDidWriteItems(result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>]) {
+    func checkTransactionDidWriteItems(_ result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>]) {
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
-        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sort(), indexes.map { $0.key }.sort())
+        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sorted(), indexes.map { $0.key }.sorted())
         XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.2 }.count, items.count)
         XCTAssertFalse(result.isEmpty)
         XCTAssertEqual(Set(result.map({$0.value})), Set(items))
     }
 
-    func checkTransactionDidReadItem(result: YapItem<TypeUnderTest, MetadataTypeUnderTest>?) -> Bool {
+    func checkTransactionDidReadItem(_ result: YapItem<TypeUnderTest, MetadataTypeUnderTest>?) -> Bool {
         guard let result = result else {
             return false
         }
@@ -127,12 +127,12 @@ class ObjectWithObjectMetadataTests: XCTestCase {
         return true
     }
 
-    func checkTransactionDidReadItems(result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>]) -> Bool {
-        if result.isEmpty {
+    func checkTransactionDidReadItems(_ result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>?]) -> Bool {
+        if result.flatMap({$0}).isEmpty {
             return false
         }
         XCTAssertEqual(Set(readTransaction.didReadAtIndexes), Set(indexes))
-        XCTAssertEqual(result.count, items.count)
+        XCTAssertEqual(result.flatMap({$0}).count, items.count)
         return true
     }
 
@@ -299,24 +299,24 @@ class Functional_Write_ObjectWithObjectMetadataTests: ObjectWithObjectMetadataTe
 
     func test__connection__async_write_item() {
         var result: YapItem<TypeUnderTest, MetadataTypeUnderTest>!
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         connection.asyncWriteWithMetadata(YapItem(item, metadata)) { tmp in
             result = tmp
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItem(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection__async_write_items() {
         var result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>] = []
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         connection.asyncWriteWithMetadata(items.yapItems(with: metadatas)) { received in
             result = received
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItems(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
@@ -351,23 +351,23 @@ class Functional_Remove_ObjectWithObjectMetadataTests: ObjectWithObjectMetadataT
     }
 
     func test__connection_async_remove_item() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingSingle()
         connection.asyncRemove(item) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItem()
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection_async_remove_items() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingMultiple()
         connection.asyncRemove(items) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItems()
         XCTAssertTrue(connection.didAsyncWrite)
     }
@@ -443,14 +443,14 @@ class Persistable_Read_ObjectWithObjectMetadataTests: ObjectWithObjectMetadataTe
     func test__reader__in_transaction_at_index_2() {
         configureForReadingSingle()
         reader = Read(readTransaction)
-        let atIndex: YapDB.Index -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataInTransactionAtIndex(readTransaction)
+        let atIndex: (YapDB.Index) -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataInTransactionAtIndex(readTransaction)
         XCTAssertTrue(checkTransactionDidReadItem(atIndex(index)))
     }
 
     func test__reader__at_index_in_transaction() {
         configureForReadingSingle()
         reader = Read(readTransaction)
-        let inTransaction: TestableReadTransaction -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataAtIndexInTransaction(index)
+        let inTransaction: (TestableReadTransaction) -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataAtIndexInTransaction(index)
         XCTAssertTrue(checkTransactionDidReadItem(inTransaction(readTransaction)))
     }
 
@@ -474,14 +474,14 @@ class Persistable_Read_ObjectWithObjectMetadataTests: ObjectWithObjectMetadataTe
     func test__reader__in_transaction_by_key_2() {
         configureForReadingSingle()
         reader = Read(readTransaction)
-        let byKey: String -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataInTransactionByKey(readTransaction)
+        let byKey: (String) -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataInTransactionByKey(readTransaction)
         XCTAssertTrue(checkTransactionDidReadItem(byKey(key)))
     }
 
     func test__reader__by_key_in_transaction() {
         configureForReadingSingle()
         reader = Read(readTransaction)
-        let inTransaction: TestableReadTransaction -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataByKeyInTransaction(key)
+        let inTransaction: (TestableReadTransaction) -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataByKeyInTransaction(key)
         XCTAssertTrue(checkTransactionDidReadItem(inTransaction(readTransaction)))
     }
 
@@ -566,8 +566,8 @@ class Persistable_Read_ObjectWithObjectMetadataTests: ObjectWithObjectMetadataTe
         reader = Read(readTransaction)
         let (items, missing): ([YapItem<TypeUnderTest, MetadataTypeUnderTest>], [String]) = reader.withMetadataFilterExisting(keys)
         XCTAssertEqual(readTransaction.didReadAtIndexes.first!, indexes.first!)
-        XCTAssertEqual(items.map { $0.value.identifier }, items.prefixUpTo(1).map { $0.value.identifier })
-        XCTAssertEqual(missing, Array(keys.suffixFrom(1)))
+        XCTAssertEqual(items.map { $0.value.identifier }, items.prefix(upTo: 1).map { $0.value.identifier })
+        XCTAssertEqual(missing, Array(keys.suffix(from: 1)))
     }
 
     // Reading - With Connection
@@ -645,8 +645,8 @@ class Persistable_Read_ObjectWithObjectMetadataTests: ObjectWithObjectMetadataTe
         let (items, missing) = reader.filterExisting(keys)
         XCTAssertTrue(connection.didRead)
         XCTAssertEqual(readTransaction.didReadAtIndexes.first!, indexes.first!)
-        XCTAssertEqual(items.map { $0.identifier }, items.prefixUpTo(1).map { $0.identifier })
-        XCTAssertEqual(missing, Array(keys.suffixFrom(1)))
+        XCTAssertEqual(items.map { $0.identifier }, items.prefix(upTo: 1).map { $0.identifier })
+        XCTAssertEqual(missing, Array(keys.suffix(from: 1)))
     }
 
 }
@@ -663,20 +663,20 @@ class Persistable_Write_ObjectWithObjectMetadataTests: ObjectWithObjectMetadataT
     }
 
     func test__item_persistable__write_async_using_connection() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         var result: YapItem<TypeUnderTest, MetadataTypeUnderTest>! = nil
 
         item.asyncWriteWithMetadata(connection, metadata: metadata) { tmp in
             result = tmp
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItem(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__item_persistable__write_using_opertion() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
 
         let operation = item.writeWithMetadataOperation(connection, metadata: metadata)
         operation.completionBlock = {
@@ -684,7 +684,7 @@ class Persistable_Write_ObjectWithObjectMetadataTests: ObjectWithObjectMetadataT
         }
 
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
         XCTAssertEqual(writeTransaction.didWriteAtIndexes[0].0, index)
         XCTAssertEqual(writeTransaction.didWriteAtIndexes[0].1.identifier, item.identifier)
@@ -702,20 +702,20 @@ class Persistable_Write_ObjectWithObjectMetadataTests: ObjectWithObjectMetadataT
     }
 
     func test__items_persistable__write_async_using_connection() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         var result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>] = []
         
         items.asyncWriteWithMetadata(connection, metadata: metadatas) { tmp in
             result = tmp
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItems(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__items_persistable__write_using_opertion() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
 
         let operation = items.writeOperation(connection)
         operation.completionBlock = {
@@ -723,9 +723,9 @@ class Persistable_Write_ObjectWithObjectMetadataTests: ObjectWithObjectMetadataT
         }
 
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
-        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sort(), indexes.map { $0.key }.sort())
+        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sorted(), indexes.map { $0.key }.sorted())
         XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.2 }.count, items.count)
         XCTAssertTrue(connection.didWrite)
     }
@@ -747,25 +747,25 @@ class Persistable_Remove_ObjectWithObjectMetadataTests: ObjectWithObjectMetadata
     }
 
     func test__connection_async_remove_item() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingSingle()
         item.asyncRemove(connection) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItem()
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection_operation_remove_item() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingSingle()
         let operation = item.removeOperation(connection)
         operation.completionBlock = {
             expectation.fulfill()
         }
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItem()
         XCTAssertTrue(connection.didWrite)
     }
@@ -785,25 +785,25 @@ class Persistable_Remove_ObjectWithObjectMetadataTests: ObjectWithObjectMetadata
     }
 
     func test__connection_async_remove_items() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingMultiple()
         items.asyncRemove(connection) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItems()
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection_operation_remove_items() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingMultiple()
         let operation = items.removeOperation(connection)
         operation.completionBlock = {
             expectation.fulfill()
         }
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItems()
         XCTAssertTrue(connection.didWrite)
     }
diff --git a/Tests/ObjectWithValueMetadataTests.swift b/Tests/ObjectWithValueMetadataTests.swift
index 7fb12a4..65336db 100644
--- a/Tests/ObjectWithValueMetadataTests.swift
+++ b/Tests/ObjectWithValueMetadataTests.swift
@@ -32,8 +32,8 @@ class ObjectWithValueMetadataTests: XCTestCase {
 
     var reader: Read<TypeUnderTest, TestableDatabase>!
 
-    var dispatchQueue: dispatch_queue_t!
-    var operationQueue: NSOperationQueue!
+    var dispatchQueue: DispatchQueue!
+    var operationQueue: OperationQueue!
 
     override func setUp() {
         super.setUp()
@@ -53,8 +53,8 @@ class ObjectWithValueMetadataTests: XCTestCase {
         connection.writeTransaction = writeTransaction
         database.connection = connection
 
-        dispatchQueue = dispatch_get_global_queue(QOS_CLASS_DEFAULT, 0)
-        operationQueue = NSOperationQueue()
+        dispatchQueue = DispatchQueue.global(qos: .default)
+        operationQueue = OperationQueue()
     }
 
     override func tearDown() {
@@ -104,7 +104,7 @@ class ObjectWithValueMetadataTests: XCTestCase {
         readTransaction.keys = keys
     }
 
-    func checkTransactionDidWriteItem(result: YapItem<TypeUnderTest, MetadataTypeUnderTest>) {
+    func checkTransactionDidWriteItem(_ result: YapItem<TypeUnderTest, MetadataTypeUnderTest>) {
         XCTAssertEqual(result.value.identifier, item.identifier)
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
         XCTAssertEqual(writeTransaction.didWriteAtIndexes[0].0, index)
@@ -112,15 +112,15 @@ class ObjectWithValueMetadataTests: XCTestCase {
         XCTAssertEqual(MetadataTypeUnderTest.decode(writeTransaction.didWriteAtIndexes[0].2), metadata)
     }
 
-    func checkTransactionDidWriteItems(result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>]) {
+    func checkTransactionDidWriteItems(_ result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>]) {
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
-        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sort(), indexes.map { $0.key }.sort())
+        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sorted(), indexes.map { $0.key }.sorted())
         XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.2 }.count, items.count)
         XCTAssertFalse(result.isEmpty)
         XCTAssertEqual(Set(result.map({$0.value})), Set(items))
     }
 
-    func checkTransactionDidReadItem(result: YapItem<TypeUnderTest, MetadataTypeUnderTest>?) -> Bool {
+    func checkTransactionDidReadItem(_ result: YapItem<TypeUnderTest, MetadataTypeUnderTest>?) -> Bool {
         guard let result = result else {
             return false
         }
@@ -131,12 +131,12 @@ class ObjectWithValueMetadataTests: XCTestCase {
         return true
     }
 
-    func checkTransactionDidReadItems(result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>]) -> Bool {
-        if result.isEmpty {
+    func checkTransactionDidReadItems(_ result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>?]) -> Bool {
+        if result.flatMap({$0}).isEmpty {
             return false
         }
         XCTAssertEqual(Set(readTransaction.didReadAtIndexes), Set(indexes))
-        XCTAssertEqual(result.count, items.count)
+        XCTAssertEqual(result.flatMap({$0}).count, items.count)
         return true
     }
 
@@ -303,24 +303,24 @@ class Functional_Write_ObjectWithValueMetadataTests: ObjectWithValueMetadataTest
 
     func test__connection__async_write_item() {
         var result: YapItem<TypeUnderTest, MetadataTypeUnderTest>!
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         connection.asyncWriteWithMetadata(YapItem(item, metadata)) { tmp in
             result = tmp
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItem(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection__async_write_items() {
         var result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>] = []
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         connection.asyncWriteWithMetadata(items.yapItems(with: metadatas)) { received in
             result = received
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItems(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
@@ -355,23 +355,23 @@ class Functional_Remove_ObjectWithValueMetadataTests: ObjectWithValueMetadataTes
     }
 
     func test__connection_async_remove_item() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingSingle()
         connection.asyncRemove(item) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItem()
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection_async_remove_items() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingMultiple()
         connection.asyncRemove(items) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItems()
         XCTAssertTrue(connection.didAsyncWrite)
     }
@@ -447,14 +447,14 @@ class Persistable_Read_ObjectWithValueMetadataTests: ObjectWithValueMetadataTest
     func test__reader__in_transaction_at_index_2() {
         configureForReadingSingle()
         reader = Read(readTransaction)
-        let atIndex: YapDB.Index -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataInTransactionAtIndex(readTransaction)
+        let atIndex: (YapDB.Index) -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataInTransactionAtIndex(readTransaction)
         XCTAssertTrue(checkTransactionDidReadItem(atIndex(index)))
     }
 
     func test__reader__at_index_in_transaction() {
         configureForReadingSingle()
         reader = Read(readTransaction)
-        let inTransaction: TestableReadTransaction -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataAtIndexInTransaction(index)
+        let inTransaction: (TestableReadTransaction) -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataAtIndexInTransaction(index)
         XCTAssertTrue(checkTransactionDidReadItem(inTransaction(readTransaction)))
     }
 
@@ -478,14 +478,14 @@ class Persistable_Read_ObjectWithValueMetadataTests: ObjectWithValueMetadataTest
     func test__reader__in_transaction_by_key_2() {
         configureForReadingSingle()
         reader = Read(readTransaction)
-        let byKey: String -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataInTransactionByKey(readTransaction)
+        let byKey: (String) -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataInTransactionByKey(readTransaction)
         XCTAssertTrue(checkTransactionDidReadItem(byKey(key)))
     }
 
     func test__reader__by_key_in_transaction() {
         configureForReadingSingle()
         reader = Read(readTransaction)
-        let inTransaction: TestableReadTransaction -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataByKeyInTransaction(key)
+        let inTransaction: (TestableReadTransaction) -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataByKeyInTransaction(key)
         XCTAssertTrue(checkTransactionDidReadItem(inTransaction(readTransaction)))
     }
 
@@ -570,8 +570,8 @@ class Persistable_Read_ObjectWithValueMetadataTests: ObjectWithValueMetadataTest
         reader = Read(readTransaction)
         let (items, missing): ([YapItem<TypeUnderTest, MetadataTypeUnderTest>], [String]) = reader.withMetadataFilterExisting(keys)
         XCTAssertEqual(readTransaction.didReadAtIndexes.first!, indexes.first!)
-        XCTAssertEqual(items.map { $0.value.identifier }, items.prefixUpTo(1).map { $0.value.identifier })
-        XCTAssertEqual(missing, Array(keys.suffixFrom(1)))
+        XCTAssertEqual(items.map { $0.value.identifier }, items.prefix(upTo: 1).map { $0.value.identifier })
+        XCTAssertEqual(missing, Array(keys.suffix(from: 1)))
     }
 
     // Reading - With Connection
@@ -649,8 +649,8 @@ class Persistable_Read_ObjectWithValueMetadataTests: ObjectWithValueMetadataTest
         let (items, missing) = reader.filterExisting(keys)
         XCTAssertTrue(connection.didRead)
         XCTAssertEqual(readTransaction.didReadAtIndexes.first!, indexes.first!)
-        XCTAssertEqual(items.map { $0.identifier }, items.prefixUpTo(1).map { $0.identifier })
-        XCTAssertEqual(missing, Array(keys.suffixFrom(1)))
+        XCTAssertEqual(items.map { $0.identifier }, items.prefix(upTo: 1).map { $0.identifier })
+        XCTAssertEqual(missing, Array(keys.suffix(from: 1)))
     }
 
 }
@@ -667,20 +667,20 @@ class Persistable_Write_ObjectWithValueMetadataTests: ObjectWithValueMetadataTes
     }
 
     func test__item_persistable__write_async_using_connection() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         var result: YapItem<TypeUnderTest, MetadataTypeUnderTest>! = nil
 
         item.asyncWriteWithMetadata(connection, metadata: metadata) { tmp in
             result = tmp
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItem(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__item_persistable__write_using_opertion() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
 
         let operation = item.writeWithMetadataOperation(connection, metadata: metadata)
         operation.completionBlock = {
@@ -688,7 +688,7 @@ class Persistable_Write_ObjectWithValueMetadataTests: ObjectWithValueMetadataTes
         }
 
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
         XCTAssertEqual(writeTransaction.didWriteAtIndexes[0].0, index)
         XCTAssertEqual(writeTransaction.didWriteAtIndexes[0].1.identifier, item.identifier)
@@ -706,20 +706,20 @@ class Persistable_Write_ObjectWithValueMetadataTests: ObjectWithValueMetadataTes
     }
 
     func test__items_persistable__write_async_using_connection() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         var result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>] = []
         
         items.asyncWriteWithMetadata(connection, metadata: metadatas) { tmp in
             result = tmp
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItems(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__items_persistable__write_using_opertion() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
 
         let operation = items.writeOperation(connection)
         operation.completionBlock = {
@@ -727,9 +727,9 @@ class Persistable_Write_ObjectWithValueMetadataTests: ObjectWithValueMetadataTes
         }
 
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
-        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sort(), indexes.map { $0.key }.sort())
+        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sorted(), indexes.map { $0.key }.sorted())
         XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.2 }.count, items.count)
         XCTAssertTrue(connection.didWrite)
     }
@@ -751,25 +751,25 @@ class Persistable_Remove_ObjectWithValueMetadataTests: ObjectWithValueMetadataTe
     }
 
     func test__connection_async_remove_item() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingSingle()
         item.asyncRemove(connection) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItem()
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection_operation_remove_item() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingSingle()
         let operation = item.removeOperation(connection)
         operation.completionBlock = {
             expectation.fulfill()
         }
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItem()
         XCTAssertTrue(connection.didWrite)
     }
@@ -789,25 +789,25 @@ class Persistable_Remove_ObjectWithValueMetadataTests: ObjectWithValueMetadataTe
     }
 
     func test__connection_async_remove_items() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingMultiple()
         items.asyncRemove(connection) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItems()
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection_operation_remove_items() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingMultiple()
         let operation = items.removeOperation(connection)
         operation.completionBlock = {
             expectation.fulfill()
         }
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItems()
         XCTAssertTrue(connection.didWrite)
     }
diff --git a/Tests/ReadWriteTests.swift b/Tests/ReadWriteTests.swift
index f526e8d..71f048c 100644
--- a/Tests/ReadWriteTests.swift
+++ b/Tests/ReadWriteTests.swift
@@ -58,8 +58,8 @@ class ReadWriteBaseTests: XCTestCase {
         ]
     }
 
-    func writeItemsToDatabase(db: YapDatabase) {
-        db.makeNewConnection().writeWithMetadata(items.yapItems(with: metadatas))
+    func writeItemsToDatabase(_ db: YapDatabase) {
+        _ = db.makeNewConnection().writeWithMetadata(items.yapItems(with: metadatas))
     }
 }
 
@@ -70,7 +70,7 @@ class ReadTests: ReadWriteBaseTests {
     func test__initialize_with_transaction() {
         let db = YapDB.testDatabase()
         let connection = db.makeNewConnection()
-        connection.readWithBlock { transaction in
+        connection.read { transaction in
             self.reader = Read(transaction)
             XCTAssertNotNil(self.reader)
         }
@@ -95,7 +95,7 @@ class ReadTests: ReadWriteBaseTests {
     func test__getting_reader_from_persistable_with_transaction() {
         let db = YapDB.testDatabase()
         let connection = db.makeNewConnection()
-        connection.readWithBlock { transaction in
+        connection.read { transaction in
             self.reader = Employee.read(transaction)
             XCTAssertNotNil(self.reader)
         }
diff --git a/Tests/Support.swift b/Tests/Support.swift
index b256da5..b0d5f66 100644
--- a/Tests/Support.swift
+++ b/Tests/Support.swift
@@ -12,7 +12,7 @@ import Foundation
 class TestableReadTransaction {
 
     var keys: [String] = []
-    var didKeysInCollection: String? = .None
+    var didKeysInCollection: String? = .none
 
     var object: AnyObject? {
         get { return objects.first }
@@ -53,7 +53,7 @@ class TestableReadTransaction {
             currentReadIndex += 1
             return object
         }
-        return .None
+        return .none
     }
 
     func getNextMetadata() -> AnyObject? {
@@ -62,23 +62,23 @@ class TestableReadTransaction {
             currentMetadataReadIndex += 1
             return object
         }
-        return .None
+        return .none
     }
 }
 
 extension TestableReadTransaction: ReadTransactionType {
 
-    func keysInCollection(collection: String) -> [String] {
+    func keysInCollection(_ collection: String) -> [String] {
         didKeysInCollection = collection
         return keys
     }
 
-    func readAtIndex(index: YapDB.Index) -> AnyObject? {
+    func readAtIndex(_ index: YapDB.Index) -> AnyObject? {
         didReadAtIndexes.append(index)
         return getNextObject()
     }
 
-    func readMetadataAtIndex(index: YapDB.Index) -> AnyObject? {
+    func readMetadataAtIndex(_ index: YapDB.Index) -> AnyObject? {
         didReadMetadataAtIndexes.append(index)
         return getNextMetadata()
     }
@@ -93,14 +93,14 @@ class TestableWriteTransaction: TestableReadTransaction {
 
 extension TestableWriteTransaction: WriteTransactionType {
 
-    func writeAtIndex(index: YapDB.Index, object: AnyObject, metadata: AnyObject?) {
+    func writeAtIndex(_ index: YapDB.Index, object: AnyObject, metadata: AnyObject?) {
         didWriteAtIndexes.append((index, object, metadata))
     }
 
     func removeAtIndexes<
-        Indexes where
-        Indexes: SequenceType,
-        Indexes.Generator.Element == YapDB.Index>(indexes: Indexes) {
+        Indexes>(_ indexes: Indexes) where
+        Indexes: Sequence,
+        Indexes.Iterator.Element == YapDB.Index {
             didRemoveAtIndexes = Array(indexes)
     }
 }
@@ -118,34 +118,34 @@ class TestableConnection {
 
 extension TestableConnection: ConnectionType {
 
-    func read<T>(block: TestableReadTransaction -> T) -> T {
+    func read<T>(_ block: @escaping (TestableReadTransaction) -> T) -> T {
         didRead = true
         return block(readTransaction)
     }
 
-    func write<T>(block: TestableWriteTransaction -> T) -> T {
+    func write<T>(_ block: @escaping (TestableWriteTransaction) -> T) -> T {
         didWrite = true
         return block(writeTransaction)
     }
 
-    func asyncRead<T>(block: TestableReadTransaction -> T, queue: dispatch_queue_t, completion: (T) -> Void) {
+    func asyncRead<T>(_ block: @escaping (TestableReadTransaction) -> T, queue: DispatchQueue, completion: @escaping (T) -> Void) {
         didAsyncRead = true
-        dispatch_async(queue) { [transaction = self.readTransaction] in
+        queue.async { [transaction = self.readTransaction] in
             completion(block(transaction))
         }
     }
 
-    func asyncWrite<T>(block: TestableWriteTransaction -> T, queue: dispatch_queue_t, completion: (T -> Void)? = .None) {
+    func asyncWrite<T>(_ block: @escaping (TestableWriteTransaction) -> T, queue: DispatchQueue, completion: ((T) -> Void)? = .none) {
         didAsyncWrite = true
-        dispatch_async(queue) { [transaction = self.writeTransaction] in
+        queue.async { [transaction = self.writeTransaction] in
             let result = block(transaction)
             completion?(result)
         }
     }
 
-    func writeBlockOperation(block: TestableWriteTransaction -> Void) -> NSOperation {
+    func writeBlockOperation(_ block: @escaping (TestableWriteTransaction) -> Void) -> Operation {
         didWriteBlockOperation = true
-        return NSBlockOperation { block(self.writeTransaction) }
+        return BlockOperation { block(self.writeTransaction) }
     }
 }
 
diff --git a/Tests/ValueWithNoMetadataTests.swift b/Tests/ValueWithNoMetadataTests.swift
index dc15538..4d1d89d 100644
--- a/Tests/ValueWithNoMetadataTests.swift
+++ b/Tests/ValueWithNoMetadataTests.swift
@@ -31,8 +31,8 @@ class ValueWithNoMetadataTests: XCTestCase {
 
     var reader: Read<TypeUnderTest, TestableDatabase>!
 
-    var dispatchQueue: dispatch_queue_t!
-    var operationQueue: NSOperationQueue!
+    var dispatchQueue: DispatchQueue!
+    var operationQueue: OperationQueue!
 
     override func setUp() {
         super.setUp()
@@ -52,8 +52,8 @@ class ValueWithNoMetadataTests: XCTestCase {
         connection.writeTransaction = writeTransaction
         database.connection = connection
 
-        dispatchQueue = dispatch_get_global_queue(QOS_CLASS_DEFAULT, 0)
-        operationQueue = NSOperationQueue()
+        dispatchQueue = DispatchQueue.global(qos: .default)
+        operationQueue = OperationQueue()
     }
 
     override func tearDown() {
@@ -74,12 +74,12 @@ class ValueWithNoMetadataTests: XCTestCase {
     }
 
     func createPersistables() {
-        item = .QRCode("I have no idea what the string of a QR Code might look like")
+        item = .qrCode("I have no idea what the string of a QR Code might look like")
         items = [
             item,
-            .UPCA(23, 42, 78, 93),
-            .QRCode("This is a different QR Code!"),
-            .UPCA(68, 59, 147, 291)
+            .upca(23, 42, 78, 93),
+            .qrCode("This is a different QR Code!"),
+            .upca(68, 59, 147, 291)
         ]
     }
 
@@ -92,7 +92,7 @@ class ValueWithNoMetadataTests: XCTestCase {
         readTransaction.keys = keys
     }
 
-    func checkTransactionDidWriteItem(result: TypeUnderTest) {
+    func checkTransactionDidWriteItem(_ result: TypeUnderTest) {
         XCTAssertEqual(result.identifier, item.identifier)
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
         XCTAssertEqual(writeTransaction.didWriteAtIndexes[0].0, index)
@@ -100,15 +100,15 @@ class ValueWithNoMetadataTests: XCTestCase {
         XCTAssertNil(writeTransaction.didWriteAtIndexes[0].2)
     }
 
-    func checkTransactionDidWriteItems(result: [TypeUnderTest]) {
+    func checkTransactionDidWriteItems(_ result: [TypeUnderTest]) {
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
-        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sort(), indexes.map { $0.key }.sort())
+        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sorted(), indexes.map { $0.key }.sorted())
         XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.2 }.count, items.count)
         XCTAssertFalse(result.isEmpty)
         XCTAssertEqual(Set(result), Set(items))
     }
 
-    func checkTransactionDidReadItem(result: TypeUnderTest?) -> Bool {
+    func checkTransactionDidReadItem(_ result: TypeUnderTest?) -> Bool {
         guard let result = result else {
             return false
         }
@@ -117,12 +117,12 @@ class ValueWithNoMetadataTests: XCTestCase {
         return true
     }
 
-    func checkTransactionDidReadItems(result: [TypeUnderTest]) -> Bool {
-        if result.isEmpty {
+    func checkTransactionDidReadItems(_ result: [TypeUnderTest?]) -> Bool {
+        if result.flatMap({$0}).isEmpty {
             return false
         }
         XCTAssertEqual(Set(readTransaction.didReadAtIndexes), Set(indexes))
-        XCTAssertEqual(result.count, items.count)
+        XCTAssertEqual(result.flatMap({$0}).count, items.count)
         return true
     }
 
@@ -289,24 +289,24 @@ class Functional_Write_ValueWithNoMetadataTests: ValueWithNoMetadataTests {
 
     func test__connection__async_write_item() {
         var result: TypeUnderTest!
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         connection.asyncWrite(item) { tmp in
             result = tmp
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItem(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection__async_write_items() {
         var result: [TypeUnderTest] = []
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         connection.asyncWrite(items) { received in
             result = received
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItems(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
@@ -341,23 +341,23 @@ class Functional_Remove_ValueWithNoMetadataTests: ValueWithNoMetadataTests {
     }
 
     func test__connection_async_remove_item() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingSingle()
         connection.asyncRemove(item) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItem()
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection_async_remove_items() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingMultiple()
         connection.asyncRemove(items) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItems()
         XCTAssertTrue(connection.didAsyncWrite)
     }
@@ -556,8 +556,8 @@ class Persistable_Read_ValueWithNoMetadataTests: ValueWithNoMetadataTests {
         reader = Read(readTransaction)
         let (items, missing) = reader.filterExisting(keys)
         XCTAssertEqual(readTransaction.didReadAtIndexes.first!, indexes.first!)
-        XCTAssertEqual(items.map { $0.identifier }, items.prefixUpTo(1).map { $0.identifier })
-        XCTAssertEqual(missing, Array(keys.suffixFrom(1)))
+        XCTAssertEqual(items.map { $0.identifier }, items.prefix(upTo: 1).map { $0.identifier })
+        XCTAssertEqual(missing, Array(keys.suffix(from: 1)))
     }
 
     // Reading - With Connection
@@ -635,8 +635,8 @@ class Persistable_Read_ValueWithNoMetadataTests: ValueWithNoMetadataTests {
         let (items, missing) = reader.filterExisting(keys)
         XCTAssertTrue(connection.didRead)
         XCTAssertEqual(readTransaction.didReadAtIndexes.first!, indexes.first!)
-        XCTAssertEqual(items.map { $0.identifier }, items.prefixUpTo(1).map { $0.identifier })
-        XCTAssertEqual(missing, Array(keys.suffixFrom(1)))
+        XCTAssertEqual(items.map { $0.identifier }, items.prefix(upTo: 1).map { $0.identifier })
+        XCTAssertEqual(missing, Array(keys.suffix(from: 1)))
     }
 
 }
@@ -653,20 +653,20 @@ class Persistable_Write_ValueWithNoMetadataTests: ValueWithNoMetadataTests {
     }
 
     func test__item_persistable__write_async_using_connection() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         var result: TypeUnderTest! = nil
 
         item.asyncWrite(connection) { tmp in
             result = tmp
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItem(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__item_persistable__write_using_opertion() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
 
         let operation = item.writeOperation(connection)
         operation.completionBlock = {
@@ -674,7 +674,7 @@ class Persistable_Write_ValueWithNoMetadataTests: ValueWithNoMetadataTests {
         }
 
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
         XCTAssertEqual(writeTransaction.didWriteAtIndexes[0].0, index)
         XCTAssertEqual(TypeUnderTest.decode(writeTransaction.didWriteAtIndexes[0].1)!, item)
@@ -692,20 +692,20 @@ class Persistable_Write_ValueWithNoMetadataTests: ValueWithNoMetadataTests {
     }
 
     func test__items_persistable__write_async_using_connection() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         var result: [TypeUnderTest] = []
         
         items.asyncWrite(connection) { tmp in
             result = tmp
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItems(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__items_persistable__write_using_opertion() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
 
         let operation = items.writeOperation(connection)
         operation.completionBlock = {
@@ -713,9 +713,9 @@ class Persistable_Write_ValueWithNoMetadataTests: ValueWithNoMetadataTests {
         }
 
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
-        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sort(), indexes.map { $0.key }.sort())
+        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sorted(), indexes.map { $0.key }.sorted())
         XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.2 }.count, items.count)
         XCTAssertTrue(connection.didWrite)
     }
@@ -737,25 +737,25 @@ class Persistable_Remove_ValueWithNoMetadataTests: ValueWithNoMetadataTests {
     }
 
     func test__connection_async_remove_item() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingSingle()
         item.asyncRemove(connection) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItem()
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection_operation_remove_item() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingSingle()
         let operation = item.removeOperation(connection)
         operation.completionBlock = {
             expectation.fulfill()
         }
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItem()
         XCTAssertTrue(connection.didWrite)
     }
@@ -775,25 +775,25 @@ class Persistable_Remove_ValueWithNoMetadataTests: ValueWithNoMetadataTests {
     }
 
     func test__connection_async_remove_items() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingMultiple()
         items.asyncRemove(connection) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItems()
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection_operation_remove_items() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingMultiple()
         let operation = items.removeOperation(connection)
         operation.completionBlock = {
             expectation.fulfill()
         }
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItems()
         XCTAssertTrue(connection.didWrite)
     }
diff --git a/Tests/ValueWithObjectMetadataTests.swift b/Tests/ValueWithObjectMetadataTests.swift
index b954985..aa3fd3d 100644
--- a/Tests/ValueWithObjectMetadataTests.swift
+++ b/Tests/ValueWithObjectMetadataTests.swift
@@ -32,8 +32,8 @@ class ValueWithObjectMetadataTests: XCTestCase {
 
     var reader: Read<TypeUnderTest, TestableDatabase>!
 
-    var dispatchQueue: dispatch_queue_t!
-    var operationQueue: NSOperationQueue!
+    var dispatchQueue: DispatchQueue!
+    var operationQueue: OperationQueue!
 
     override func setUp() {
         super.setUp()
@@ -53,8 +53,8 @@ class ValueWithObjectMetadataTests: XCTestCase {
         connection.writeTransaction = writeTransaction
         database.connection = connection
 
-        dispatchQueue = dispatch_get_global_queue(QOS_CLASS_DEFAULT, 0)
-        operationQueue = NSOperationQueue()
+        dispatchQueue = DispatchQueue.global(qos: .default)
+        operationQueue = OperationQueue()
     }
 
     override func tearDown() {
@@ -81,30 +81,30 @@ class ValueWithObjectMetadataTests: XCTestCase {
             Product(
                 identifier: "vodka-123",
                 name: "Belvidere",
-                barcode: .UPCA(1, 2, 3, 4)
+                barcode: .upca(1, 2, 3, 4)
             ),
             Product(
                 identifier: "gin-123",
                 name: "Boxer Gin",
-                barcode: .UPCA(5, 10, 15, 20)
+                barcode: .upca(5, 10, 15, 20)
                 ),
             Product(
                 identifier: "rum-123",
                 name: "Mount Gay Rum",
-                barcode: .UPCA(12, 24, 39, 48)
+                barcode: .upca(12, 24, 39, 48)
                 ),
             Product(
                 identifier: "gin-234",
                 name: "Monkey 47",
-                barcode: .UPCA(31, 62, 93, 124)
+                barcode: .upca(31, 62, 93, 124)
                 )
             ]
 
         metadatas = [
-            NSNumber(integer: 12),
-            NSNumber(integer: 13),
-            NSNumber(integer: 14),
-            NSNumber(integer: 15)
+            NSNumber(value: 12 as Int),
+            NSNumber(value: 13 as Int),
+            NSNumber(value: 14 as Int),
+            NSNumber(value: 15 as Int)
         ]
         items = products.map { TypeUnderTest(product: $0) }
         item = items[0]
@@ -122,7 +122,7 @@ class ValueWithObjectMetadataTests: XCTestCase {
         readTransaction.keys = keys
     }
 
-    func checkTransactionDidWriteItem(result: YapItem<TypeUnderTest, MetadataTypeUnderTest>) {
+    func checkTransactionDidWriteItem(_ result: YapItem<TypeUnderTest, MetadataTypeUnderTest>) {
         XCTAssertEqual(result.value.identifier, item.identifier)
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
         XCTAssertEqual(writeTransaction.didWriteAtIndexes[0].0, index)
@@ -130,15 +130,15 @@ class ValueWithObjectMetadataTests: XCTestCase {
         XCTAssertEqual(writeTransaction.didWriteAtIndexes[0].2 as? NSNumber, metadata)
     }
 
-    func checkTransactionDidWriteItems(result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>]) {
+    func checkTransactionDidWriteItems(_ result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>]) {
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
-        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sort(), indexes.map { $0.key }.sort())
+        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sorted(), indexes.map { $0.key }.sorted())
         XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.2 }.count, items.count)
         XCTAssertFalse(result.isEmpty)
         XCTAssertEqual(Set(result.map({$0.value})), Set(items))
     }
 
-    func checkTransactionDidReadItem(result: YapItem<TypeUnderTest, MetadataTypeUnderTest>?) -> Bool {
+    func checkTransactionDidReadItem(_ result: YapItem<TypeUnderTest, MetadataTypeUnderTest>?) -> Bool {
         XCTAssertEqual(readTransaction.didReadAtIndex, index)
         guard let result = result else {
             return false
@@ -149,16 +149,16 @@ class ValueWithObjectMetadataTests: XCTestCase {
         return true
     }
 
-    func checkTransactionDidReadItems(result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>]) -> Bool {
-        if result.isEmpty {
+    func checkTransactionDidReadItems(_ result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>?]) -> Bool {
+        if result.flatMap({$0}).isEmpty {
             return false
         }
         XCTAssertEqual(Set(readTransaction.didReadAtIndexes), Set(indexes))
-        XCTAssertEqual(result.count, items.count)
+        XCTAssertEqual(result.flatMap({$0}).count, items.count)
         return true
     }
 
-    func checkTransactionDidReadMetadataItem(result: MetadataTypeUnderTest?) -> Bool {
+    func checkTransactionDidReadMetadataItem(_ result: MetadataTypeUnderTest?) -> Bool {
         XCTAssertNil(readTransaction.didReadAtIndex)
         guard let result = result else {
             return false
@@ -168,13 +168,13 @@ class ValueWithObjectMetadataTests: XCTestCase {
         return true
     }
 
-    func checkTransactionDidReadMetadataItems(result: [MetadataTypeUnderTest]) -> Bool {
+    func checkTransactionDidReadMetadataItems(_ result: [MetadataTypeUnderTest?]) -> Bool {
         XCTAssertTrue(readTransaction.didReadAtIndexes.isEmpty)
-        if result.isEmpty {
+        if result.flatMap({$0}).isEmpty {
             return false
         }
         XCTAssertEqual(Set(readTransaction.didReadMetadataAtIndexes), Set(indexes))
-        XCTAssertEqual(result.count, items.count)
+        XCTAssertEqual(result.flatMap({$0}).count, items.count)
         return true
     }
 
@@ -385,24 +385,24 @@ class Functional_Write_ValueWithObjectMetadataTests: ValueWithObjectMetadataTest
 
     func test__connection__async_write_item() {
         var result: YapItem<TypeUnderTest, MetadataTypeUnderTest>!
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         connection.asyncWriteWithMetadata(YapItem(item, metadata)) { tmp in
             result = tmp
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItem(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection__async_write_items() {
         var result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>] = []
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         connection.asyncWriteWithMetadata(items.yapItems(with: metadatas)) { received in
             result = received
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItems(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
@@ -437,23 +437,23 @@ class Functional_Remove_ValueWithObjectMetadataTests: ValueWithObjectMetadataTes
     }
 
     func test__connection_async_remove_item() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingSingle()
         connection.asyncRemove(item) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItem()
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection_async_remove_items() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingMultiple()
         connection.asyncRemove(items) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItems()
         XCTAssertTrue(connection.didAsyncWrite)
     }
@@ -529,14 +529,14 @@ class Persistable_Read_ValueWithObjectMetadataTests: ValueWithObjectMetadataTest
     func test__reader__in_transaction_at_index_2() {
         configureForReadingSingle()
         reader = Read(readTransaction)
-        let atIndex: YapDB.Index -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataInTransactionAtIndex(readTransaction)
+        let atIndex: (YapDB.Index) -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataInTransactionAtIndex(readTransaction)
         XCTAssertTrue(checkTransactionDidReadItem(atIndex(index)))
     }
 
     func test__reader__at_index_in_transaction() {
         configureForReadingSingle()
         reader = Read(readTransaction)
-        let inTransaction: TestableReadTransaction -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataAtIndexInTransaction(index)
+        let inTransaction: (TestableReadTransaction) -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataAtIndexInTransaction(index)
         XCTAssertTrue(checkTransactionDidReadItem(inTransaction(readTransaction)))
     }
 
@@ -560,14 +560,14 @@ class Persistable_Read_ValueWithObjectMetadataTests: ValueWithObjectMetadataTest
     func test__reader__in_transaction_by_key_2() {
         configureForReadingSingle()
         reader = Read(readTransaction)
-        let byKey: String -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataInTransactionByKey(readTransaction)
+        let byKey: (String) -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataInTransactionByKey(readTransaction)
         XCTAssertTrue(checkTransactionDidReadItem(byKey(key)))
     }
 
     func test__reader__by_key_in_transaction() {
         configureForReadingSingle()
         reader = Read(readTransaction)
-        let inTransaction: TestableReadTransaction -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataByKeyInTransaction(key)
+        let inTransaction: (TestableReadTransaction) -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataByKeyInTransaction(key)
         XCTAssertTrue(checkTransactionDidReadItem(inTransaction(readTransaction)))
     }
 
@@ -652,8 +652,8 @@ class Persistable_Read_ValueWithObjectMetadataTests: ValueWithObjectMetadataTest
         reader = Read(readTransaction)
         let (items, missing): ([YapItem<TypeUnderTest, MetadataTypeUnderTest>], [String]) = reader.withMetadataFilterExisting(keys)
         XCTAssertEqual(readTransaction.didReadAtIndexes.first!, indexes.first!)
-        XCTAssertEqual(items.map { $0.value.identifier }, items.prefixUpTo(1).map { $0.value.identifier })
-        XCTAssertEqual(missing, Array(keys.suffixFrom(1)))
+        XCTAssertEqual(items.map { $0.value.identifier }, items.prefix(upTo: 1).map { $0.value.identifier })
+        XCTAssertEqual(missing, Array(keys.suffix(from: 1)))
     }
 
     // Reading - With Connection
@@ -731,8 +731,8 @@ class Persistable_Read_ValueWithObjectMetadataTests: ValueWithObjectMetadataTest
         let (items, missing) = reader.filterExisting(keys)
         XCTAssertTrue(connection.didRead)
         XCTAssertEqual(readTransaction.didReadAtIndexes.first!, indexes.first!)
-        XCTAssertEqual(items.map { $0.identifier }, items.prefixUpTo(1).map { $0.identifier })
-        XCTAssertEqual(missing, Array(keys.suffixFrom(1)))
+        XCTAssertEqual(items.map { $0.identifier }, items.prefix(upTo: 1).map { $0.identifier })
+        XCTAssertEqual(missing, Array(keys.suffix(from: 1)))
     }
 
 }
@@ -800,20 +800,20 @@ class Persistable_Write_ValueWithObjectMetadataTests: ValueWithObjectMetadataTes
     }
 
     func test__item_persistable__write_async_using_connection() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         var result: YapItem<TypeUnderTest, MetadataTypeUnderTest>! = nil
 
         item.asyncWriteWithMetadata(connection, metadata: metadata) { tmp in
             result = tmp
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItem(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__item_persistable__write_using_opertion() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
 
         let operation = item.writeWithMetadataOperation(connection, metadata: metadata)
         operation.completionBlock = {
@@ -821,7 +821,7 @@ class Persistable_Write_ValueWithObjectMetadataTests: ValueWithObjectMetadataTes
         }
 
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
         XCTAssertEqual(writeTransaction.didWriteAtIndexes[0].0, index)
         XCTAssertEqual(TypeUnderTest.decode(writeTransaction.didWriteAtIndexes[0].1)!, item)
@@ -839,20 +839,20 @@ class Persistable_Write_ValueWithObjectMetadataTests: ValueWithObjectMetadataTes
     }
 
     func test__items_persistable__write_async_using_connection() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         var result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>] = []
         
         items.asyncWriteWithMetadata(connection, metadata: metadatas) { tmp in
             result = tmp
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItems(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__items_persistable__write_using_opertion() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
 
         let operation = items.writeWithMetadataOperation(connection, metadata: metadatas)
         operation.completionBlock = {
@@ -860,9 +860,9 @@ class Persistable_Write_ValueWithObjectMetadataTests: ValueWithObjectMetadataTes
         }
 
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
-        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sort(), indexes.map { $0.key }.sort())
+        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sorted(), indexes.map { $0.key }.sorted())
         XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.2 }.count, items.count)
         XCTAssertTrue(connection.didWrite)
     }    
@@ -884,25 +884,25 @@ class Persistable_Remove_ValueWithObjectMetadataTests: ValueWithObjectMetadataTe
     }
 
     func test__connection_async_remove_item() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingSingle()
         item.asyncRemove(connection) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItem()
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection_operation_remove_item() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingSingle()
         let operation = item.removeOperation(connection)
         operation.completionBlock = {
             expectation.fulfill()
         }
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItem()
         XCTAssertTrue(connection.didWrite)
     }
@@ -922,25 +922,25 @@ class Persistable_Remove_ValueWithObjectMetadataTests: ValueWithObjectMetadataTe
     }
 
     func test__connection_async_remove_items() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingMultiple()
         items.asyncRemove(connection) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItems()
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection_operation_remove_items() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingMultiple()
         let operation = items.removeOperation(connection)
         operation.completionBlock = {
             expectation.fulfill()
         }
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItems()
         XCTAssertTrue(connection.didWrite)
     }
diff --git a/Tests/ValueWithValueMetadataTests.swift b/Tests/ValueWithValueMetadataTests.swift
index 4b1b257..5453217 100644
--- a/Tests/ValueWithValueMetadataTests.swift
+++ b/Tests/ValueWithValueMetadataTests.swift
@@ -32,8 +32,8 @@ class ValueWithValueMetadataTests: XCTestCase {
 
     var reader: Read<TypeUnderTest, TestableDatabase>!
 
-    var dispatchQueue: dispatch_queue_t!
-    var operationQueue: NSOperationQueue!
+    var dispatchQueue: DispatchQueue!
+    var operationQueue: OperationQueue!
 
     override func setUp() {
         super.setUp()
@@ -53,8 +53,8 @@ class ValueWithValueMetadataTests: XCTestCase {
         connection.writeTransaction = writeTransaction
         database.connection = connection
 
-        dispatchQueue = dispatch_get_global_queue(QOS_CLASS_DEFAULT, 0)
-        operationQueue = NSOperationQueue()
+        dispatchQueue = DispatchQueue.global(qos: .default)
+        operationQueue = OperationQueue()
     }
 
     override func tearDown() {
@@ -80,7 +80,7 @@ class ValueWithValueMetadataTests: XCTestCase {
         item = TypeUnderTest(
             identifier: "vodka-123",
             name: "Belvidere",
-            barcode: .UPCA(1, 2, 3, 4)
+            barcode: .upca(1, 2, 3, 4)
         )
         metadata = TypeUnderTest.Metadata(categoryIdentifier: 1)
         items = [
@@ -88,17 +88,17 @@ class ValueWithValueMetadataTests: XCTestCase {
             TypeUnderTest(
                 identifier: "gin-123",
                 name: "Boxer Gin",
-                barcode: .UPCA(5, 10, 15, 20)
+                barcode: .upca(5, 10, 15, 20)
             ),
             TypeUnderTest(
                 identifier: "rum-123",
                 name: "Mount Gay Rum",
-                barcode: .UPCA(12, 24, 39, 48)
+                barcode: .upca(12, 24, 39, 48)
             ),
             TypeUnderTest(
                 identifier: "gin-234",
                 name: "Monkey 47",
-                barcode: .UPCA(31, 62, 93, 124)
+                barcode: .upca(31, 62, 93, 124)
             )
         ]
         metadatas = [
@@ -120,7 +120,7 @@ class ValueWithValueMetadataTests: XCTestCase {
         readTransaction.keys = keys
     }
 
-    func checkTransactionDidWriteItem(result: YapItem<TypeUnderTest, MetadataTypeUnderTest>) {
+    func checkTransactionDidWriteItem(_ result: YapItem<TypeUnderTest, MetadataTypeUnderTest>) {
         XCTAssertEqual(result.value.identifier, item.identifier)
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
         XCTAssertEqual(writeTransaction.didWriteAtIndexes[0].0, index)
@@ -128,15 +128,15 @@ class ValueWithValueMetadataTests: XCTestCase {
         XCTAssertEqual(MetadataTypeUnderTest.decode(writeTransaction.didWriteAtIndexes[0].2), metadata)
     }
 
-    func checkTransactionDidWriteItems(result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>]) {
+    func checkTransactionDidWriteItems(_ result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>]) {
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
-        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sort(), indexes.map { $0.key }.sort())
+        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sorted(), indexes.map { $0.key }.sorted())
         XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.2 }.count, items.count)
         XCTAssertFalse(result.isEmpty)
         XCTAssertEqual(Set(result.map({$0.value})), Set(items))
     }
 
-    func checkTransactionDidReadItem(result: YapItem<TypeUnderTest, MetadataTypeUnderTest>?) -> Bool {
+    func checkTransactionDidReadItem(_ result: YapItem<TypeUnderTest, MetadataTypeUnderTest>?) -> Bool {
         XCTAssertEqual(readTransaction.didReadAtIndex, index)
         guard let result = result else {
             return false
@@ -147,16 +147,16 @@ class ValueWithValueMetadataTests: XCTestCase {
         return true
     }
 
-    func checkTransactionDidReadItems(result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>]) -> Bool {
-        if result.isEmpty {
+    func checkTransactionDidReadItems(_ result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>?]) -> Bool {
+        if result.flatMap({$0}).isEmpty {
             return false
         }
         XCTAssertEqual(Set(readTransaction.didReadAtIndexes), Set(indexes))
-        XCTAssertEqual(result.count, items.count)
+        XCTAssertEqual(result.flatMap({$0}).count, items.count)
         return true
     }
 
-    func checkTransactionDidReadMetadataItem(result: MetadataTypeUnderTest?) -> Bool {
+    func checkTransactionDidReadMetadataItem(_ result: MetadataTypeUnderTest?) -> Bool {
         XCTAssertNil(readTransaction.didReadAtIndex)
         guard let result = result else {
             return false
@@ -166,13 +166,13 @@ class ValueWithValueMetadataTests: XCTestCase {
         return true
     }
 
-    func checkTransactionDidReadMetadataItems(result: [MetadataTypeUnderTest]) -> Bool {
+    func checkTransactionDidReadMetadataItems(_ result: [MetadataTypeUnderTest?]) -> Bool {
         XCTAssertTrue(readTransaction.didReadAtIndexes.isEmpty)
-        if result.isEmpty {
+        if result.flatMap({$0}).isEmpty {
             return false
         }
         XCTAssertEqual(Set(readTransaction.didReadMetadataAtIndexes), Set(indexes))
-        XCTAssertEqual(result.count, items.count)
+        XCTAssertEqual(result.flatMap({$0}).count, items.count)
         return true
     }
 
@@ -382,24 +382,24 @@ class Functional_Write_ValueWithValueMetadataTests: ValueWithValueMetadataTests
 
     func test__connection__async_write_item() {
         var result: YapItem<TypeUnderTest, MetadataTypeUnderTest>!
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         connection.asyncWriteWithMetadata(YapItem(item, metadata)) { tmp in
             result = tmp
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItem(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection__async_write_items() {
         var result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>] = []
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         connection.asyncWriteWithMetadata(items.yapItems(with: metadatas)) { received in
             result = received
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItems(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
@@ -434,23 +434,23 @@ class Functional_Remove_ValueWithValueMetadataTests: ValueWithValueMetadataTests
     }
 
     func test__connection_async_remove_item() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingSingle()
         connection.asyncRemove(item) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItem()
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection_async_remove_items() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingMultiple()
         connection.asyncRemove(items) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItems()
         XCTAssertTrue(connection.didAsyncWrite)
     }
@@ -526,14 +526,14 @@ class Persistable_Read_ValueWithValueMetadataTests: ValueWithValueMetadataTests
     func test__reader__in_transaction_at_index_2() {
         configureForReadingSingle()
         reader = Read(readTransaction)
-        let atIndex: YapDB.Index -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataInTransactionAtIndex(readTransaction)
+        let atIndex: (YapDB.Index) -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataInTransactionAtIndex(readTransaction)
         XCTAssertTrue(checkTransactionDidReadItem(atIndex(index)))
     }
 
     func test__reader__at_index_in_transaction() {
         configureForReadingSingle()
         reader = Read(readTransaction)
-        let inTransaction: TestableReadTransaction -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataAtIndexInTransaction(index)
+        let inTransaction: (TestableReadTransaction) -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataAtIndexInTransaction(index)
         XCTAssertTrue(checkTransactionDidReadItem(inTransaction(readTransaction)))
     }
 
@@ -557,14 +557,14 @@ class Persistable_Read_ValueWithValueMetadataTests: ValueWithValueMetadataTests
     func test__reader__in_transaction_by_key_2() {
         configureForReadingSingle()
         reader = Read(readTransaction)
-        let byKey: String -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataInTransactionByKey(readTransaction)
+        let byKey: (String) -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataInTransactionByKey(readTransaction)
         XCTAssertTrue(checkTransactionDidReadItem(byKey(key)))
     }
 
     func test__reader__by_key_in_transaction() {
         configureForReadingSingle()
         reader = Read(readTransaction)
-        let inTransaction: TestableReadTransaction -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataByKeyInTransaction(key)
+        let inTransaction: (TestableReadTransaction) -> YapItem<TypeUnderTest, MetadataTypeUnderTest>? = reader.withMetadataByKeyInTransaction(key)
         XCTAssertTrue(checkTransactionDidReadItem(inTransaction(readTransaction)))
     }
 
@@ -649,8 +649,8 @@ class Persistable_Read_ValueWithValueMetadataTests: ValueWithValueMetadataTests
         reader = Read(readTransaction)
         let (items, missing): ([YapItem<TypeUnderTest, MetadataTypeUnderTest>], [String]) = reader.withMetadataFilterExisting(keys)
         XCTAssertEqual(readTransaction.didReadAtIndexes.first!, indexes.first!)
-        XCTAssertEqual(items.map { $0.value.identifier }, items.prefixUpTo(1).map { $0.value.identifier })
-        XCTAssertEqual(missing, Array(keys.suffixFrom(1)))
+        XCTAssertEqual(items.map { $0.value.identifier }, items.prefix(upTo: 1).map { $0.value.identifier })
+        XCTAssertEqual(missing, Array(keys.suffix(from: 1)))
     }
 
     // Reading - With Connection
@@ -728,8 +728,8 @@ class Persistable_Read_ValueWithValueMetadataTests: ValueWithValueMetadataTests
         let (items, missing) = reader.filterExisting(keys)
         XCTAssertTrue(connection.didRead)
         XCTAssertEqual(readTransaction.didReadAtIndexes.first!, indexes.first!)
-        XCTAssertEqual(items.map { $0.identifier }, items.prefixUpTo(1).map { $0.identifier })
-        XCTAssertEqual(missing, Array(keys.suffixFrom(1)))
+        XCTAssertEqual(items.map { $0.identifier }, items.prefix(upTo: 1).map { $0.identifier })
+        XCTAssertEqual(missing, Array(keys.suffix(from: 1)))
     }
 
 }
@@ -797,20 +797,20 @@ class Persistable_Write_ValueWithValueMetadataTests: ValueWithValueMetadataTests
     }
 
     func test__item_persistable__write_async_using_connection() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         var result: YapItem<TypeUnderTest, MetadataTypeUnderTest>! = nil
 
         item.asyncWriteWithMetadata(connection, metadata: metadata) { tmp in
             result = tmp
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItem(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__item_persistable__write_using_opertion() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
 
         let operation = item.writeWithMetadataOperation(connection, metadata: metadata)
         operation.completionBlock = {
@@ -818,7 +818,7 @@ class Persistable_Write_ValueWithValueMetadataTests: ValueWithValueMetadataTests
         }
 
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
         XCTAssertEqual(writeTransaction.didWriteAtIndexes[0].0, index)
         XCTAssertEqual(TypeUnderTest.decode(writeTransaction.didWriteAtIndexes[0].1)!, item)
@@ -836,20 +836,20 @@ class Persistable_Write_ValueWithValueMetadataTests: ValueWithValueMetadataTests
     }
 
     func test__items_persistable__write_async_using_connection() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         var result: [YapItem<TypeUnderTest, MetadataTypeUnderTest>] = []
 
         items.asyncWriteWithMetadata(connection, metadata: metadatas) { tmp in
             result = tmp
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidWriteItems(result)
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__items_persistable__write_using_opertion() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
 
         let operation = items.writeWithMetadataOperation(connection, metadata: metadatas)
         operation.completionBlock = {
@@ -857,9 +857,9 @@ class Persistable_Write_ValueWithValueMetadataTests: ValueWithValueMetadataTests
         }
 
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         XCTAssertFalse(writeTransaction.didWriteAtIndexes.isEmpty)
-        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sort(), indexes.map { $0.key }.sort())
+        XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.0.key }.sorted(), indexes.map { $0.key }.sorted())
         XCTAssertEqual(writeTransaction.didWriteAtIndexes.map { $0.2 }.count, items.count)
         XCTAssertTrue(connection.didWrite)
     }
@@ -881,25 +881,25 @@ class Persistable_Remove_ValueWithValueMetadataTests: ValueWithValueMetadataTest
     }
 
     func test__connection_async_remove_item() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingSingle()
         item.asyncRemove(connection) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItem()
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection_operation_remove_item() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingSingle()
         let operation = item.removeOperation(connection)
         operation.completionBlock = {
             expectation.fulfill()
         }
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItem()
         XCTAssertTrue(connection.didWrite)
     }
@@ -919,25 +919,25 @@ class Persistable_Remove_ValueWithValueMetadataTests: ValueWithValueMetadataTest
     }
 
     func test__connection_async_remove_items() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingMultiple()
         items.asyncRemove(connection) {
             expectation.fulfill()
         }
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItems()
         XCTAssertTrue(connection.didAsyncWrite)
     }
 
     func test__connection_operation_remove_items() {
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
         configureForReadingMultiple()
         let operation = items.removeOperation(connection)
         operation.completionBlock = {
             expectation.fulfill()
         }
         operationQueue.addOperation(operation)
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
         checkTransactionDidRemoveItems()
         XCTAssertTrue(connection.didWrite)
     }
diff --git a/Tests/YapDatabaseExtensionsTests.swift b/Tests/YapDatabaseExtensionsTests.swift
index b244ca2..b14886a 100644
--- a/Tests/YapDatabaseExtensionsTests.swift
+++ b/Tests/YapDatabaseExtensionsTests.swift
@@ -66,7 +66,7 @@ class YapDatabaseReadTransactionTests: ReadWriteBaseTests {
         writeItemsToDatabase(db)
         let keys = db.makeNewConnection().read { $0.keysInCollection(Employee.collection) }
         XCTAssertNotNil(keys)
-        XCTAssertEqual(keys.sort(), items.map { $0.key }.sort())
+        XCTAssertEqual(keys.sorted(), items.map { $0.key }.sorted())
     }
 
     func test__read_at_index_returns_nil_with_empty_db() {
@@ -101,7 +101,7 @@ class YapDatabaseReadWriteTransactionTests: ReadWriteBaseTests {
 
     func test__write_at_index_without_metadata() {
         let db = YapDB.testDatabase()
-        db.makeNewConnection().readWriteWithBlock { transaction in
+        db.makeNewConnection().readWrite { transaction in
             transaction.writeAtIndex(self.index, object: self.item)
         }
         let written = Employee.read(db).atIndex(index)
@@ -111,7 +111,7 @@ class YapDatabaseReadWriteTransactionTests: ReadWriteBaseTests {
 
     func test__write_at_index_with_metadata() {
         let db = YapDB.testDatabase()
-        db.makeNewConnection().readWriteWithBlock { transaction in
+        db.makeNewConnection().readWrite { transaction in
             transaction.writeAtIndex(self.index, object: self.item, metadata: self.metadata)
         }
         let written: YapItem<Employee, NSDate>? = Employee.read(db).withMetadataAtIndex(index)
@@ -123,10 +123,10 @@ class YapDatabaseReadWriteTransactionTests: ReadWriteBaseTests {
     func test__remove_at_indexes() {
         let db = YapDB.testDatabase()
 
-        db.makeNewConnection().write(items)
+        _ = db.makeNewConnection().write(items)
         XCTAssertNotNil(Employee.read(db).atIndex(index))
 
-        db.makeNewConnection().readWriteWithBlock { transaction in
+        db.makeNewConnection().readWrite { transaction in
             transaction.removeAtIndexes(self.indexes)
         }
 
@@ -136,23 +136,23 @@ class YapDatabaseReadWriteTransactionTests: ReadWriteBaseTests {
 
 class YapDatabaseConnectionTests: ReadWriteBaseTests {
 
-    var dispatchQueue: dispatch_queue_t!
-    var operationQueue: NSOperationQueue!
+    var dispatchQueue: DispatchQueue!
+    var operationQueue: OperationQueue!
 
     override func setUp() {
         super.setUp()
-        dispatchQueue = dispatch_get_global_queue(QOS_CLASS_DEFAULT, 0)
-        operationQueue = NSOperationQueue()
+        dispatchQueue = DispatchQueue.global(qos: .default)
+        operationQueue = OperationQueue()
     }
 
     func test__async_read() {
         let db = YapDB.testDatabase()
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
 
-        db.makeNewConnection().write(item)
+        _ = db.makeNewConnection().write(item)
         XCTAssertNotNil(Employee.read(db).atIndex(index))
 
-        var received: Employee? = .None
+        var received: Employee? = .none
         db.newConnection().asyncRead({ transaction -> Employee? in
             return transaction.readAtIndex(self.index) as? Employee
         }, queue: dispatchQueue) { (result: Employee?) in
@@ -160,16 +160,16 @@ class YapDatabaseConnectionTests: ReadWriteBaseTests {
             expectation.fulfill()
         }
 
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
 
         XCTAssertNotNil(received)
     }
 
     func test__async_write() {
         let db = YapDB.testDatabase()
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
 
-        var written: Employee? = .None
+        var written: Employee? = .none
         db.makeNewConnection().asyncWrite({ transaction -> Employee? in
             transaction.writeAtIndex(self.index, object: self.item, metadata: self.metadata)
             return self.item
@@ -178,7 +178,7 @@ class YapDatabaseConnectionTests: ReadWriteBaseTests {
             expectation.fulfill()
         }
 
-        waitForExpectationsWithTimeout(3.0, handler: nil)
+        waitForExpectations(timeout: 3.0, handler: nil)
 
         XCTAssertNotNil(written)
         XCTAssertNotNil(Employee.read(db).atIndex(index))
@@ -186,7 +186,7 @@ class YapDatabaseConnectionTests: ReadWriteBaseTests {
 
     func test__writeBlockOperation() {
         let db = YapDB.testDatabase()
-        let expectation = expectationWithDescription("Test: \(#function)")
+        let expectation = self.expectation(description: "Test: \(#function)")
 
         var didExecuteWithTransaction = false
         let operation = db.makeNewConnection().writeBlockOperation { transaction in
@@ -196,8 +196,8 @@ class YapDatabaseConnectionTests: ReadWriteBaseTests {
 
         operationQueue.addOperation(operation)
 
-        waitForExpectationsWithTimeout(3.0, handler: nil)
-        XCTAssertTrue(operation.finished)
+        waitForExpectations(timeout: 3.0, handler: nil)
+        XCTAssertTrue(operation.isFinished)
         XCTAssertTrue(didExecuteWithTransaction)
     }
 }
@@ -240,7 +240,7 @@ class ValueCodingTests: XCTestCase {
         item = Product(
             identifier: "vodka-123",
             name: "Belvidere",
-            barcode: .UPCA(1, 2, 3, 4)
+            barcode: .upca(1, 2, 3, 4)
         )
         metadata = Product.Metadata(categoryIdentifier: 1)
         items = [
@@ -248,17 +248,17 @@ class ValueCodingTests: XCTestCase {
             Product(
                 identifier: "gin-123",
                 name: "Boxer Gin",
-                barcode: .UPCA(5, 10, 15, 20)
+                barcode: .upca(5, 10, 15, 20)
             ),
             Product(
                 identifier: "rum-123",
                 name: "Mount Gay Rum",
-                barcode: .UPCA(12, 24, 39, 48)
+                barcode: .upca(12, 24, 39, 48)
             ),
             Product(
                 identifier: "gin-234",
                 name: "Monkey 47",
-                barcode: .UPCA(31, 62, 93, 124)
+                barcode: .upca(31, 62, 93, 124)
             )
         ]
         metadatas = [
@@ -280,11 +280,11 @@ class ValueCodingTests: XCTestCase {
 
     func test__index_is_codable() {
         let db = YapDB.testDatabase()
-        db.makeNewConnection().readWriteWithBlock { transaction in
+        db.makeNewConnection().readWrite { transaction in
             transaction.setObject(self.index.encoded, forKey: "test-index", inCollection: "test-index-collection")
         }
 
-        let unarchived = YapDB.Index.decode(db.makeNewConnection().read { $0.objectForKey("test-index", inCollection: "test-index-collection") })
+        let unarchived = YapDB.Index.decode(db.makeNewConnection().read { $0.object(forKey: "test-index", inCollection: "test-index-collection") })
         XCTAssertNotNil(unarchived)
         XCTAssertEqual(unarchived!, index)
     }
diff --git a/YapDatabaseExtensions.xcodeproj/project.pbxproj b/YapDatabaseExtensions.xcodeproj/project.pbxproj
index 00e948c..dd69886 100644
--- a/YapDatabaseExtensions.xcodeproj/project.pbxproj
+++ b/YapDatabaseExtensions.xcodeproj/project.pbxproj
@@ -270,11 +270,11 @@
 				TargetAttributes = {
 					656BAE6F1D9A4CCC008279EE = {
 						CreatedOnToolsVersion = 7.3.1;
-						LastSwiftMigration = 0800;
+						LastSwiftMigration = 0820;
 					};
 					656BAE791D9A4CCC008279EE = {
 						CreatedOnToolsVersion = 7.3.1;
-						LastSwiftMigration = 0800;
+						LastSwiftMigration = 0820;
 					};
 				};
 			};
@@ -323,7 +323,6 @@
 				ValueCoding,
 				YapDatabase,
 				CocoaLumberjack,
-				Reachability,
 			);
 			name = "Copy Carthage Frameworks";
 			outputPaths = (
@@ -497,7 +496,7 @@
 				ONLY_ACTIVE_ARCH = YES;
 				SKIP_INSTALL = YES;
 				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
-				SWIFT_VERSION = 2.3;
+				SWIFT_VERSION = 3.0;
 				VERSIONING_SYSTEM = "apple-generic";
 				VERSION_INFO_PREFIX = "";
 			};
@@ -543,7 +542,7 @@
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/../Frameworks @loader_path/Frameworks";
 				MTL_ENABLE_DEBUG_INFO = NO;
 				SKIP_INSTALL = YES;
-				SWIFT_VERSION = 2.3;
+				SWIFT_VERSION = 3.0;
 				VERSIONING_SYSTEM = "apple-generic";
 				VERSION_INFO_PREFIX = "";
 			};
@@ -593,7 +592,7 @@
 				ONLY_ACTIVE_ARCH = YES;
 				SDKROOT = macosx;
 				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
-				SWIFT_VERSION = 2.3;
+				SWIFT_VERSION = 3.0;
 			};
 			name = Debug;
 		};
@@ -633,7 +632,7 @@
 				MACOSX_DEPLOYMENT_TARGET = 10.11;
 				MTL_ENABLE_DEBUG_INFO = NO;
 				SDKROOT = macosx;
-				SWIFT_VERSION = 2.3;
+				SWIFT_VERSION = 3.0;
 			};
 			name = Release;
 		};