Answer:
- Key Value Observing is a process of observing changes of an object.
- KVO helps to update the UI when there is a change in the property value that is displayed in the user interface.
Answer:
- Key Value Coding is a process of alternate way to access Properties of a Class
class BankAccount: NSObject {
@objc dynamic var balance: Int = 0
func deductAnnumalMaintenance() {
balance -= 25
}
func depositAmount(amount: Int) {
balance += amount
}
func withdrawAmount(amount: Int) {
balance -= amount
}
}
class Human: NSObject {
@objc var myAccount: BankAccount = BankAccount()
var observer: NSKeyValueObservation?
func observeChangesInMyBalance() {
self.observer = self.observe(\.myAccount.balance, options: [.old, .new]) { human, change in
print(change)
}
}
deinit {
observer?.invalidate()
}
}
let human: Human = Human()
human.observeChangesInMyBalance()
human.myAccount.deductAnnumalMaintenance()
// NSKeyValueObservedChange<Int>(kind: __C.NSKeyValueChange, newValue: Optional(-25), oldValue: Optional(0), indexes: nil, isPrior: false)
human.myAccount.depositAmount(amount: 300)
// NSKeyValueObservedChange<Int>(kind: __C.NSKeyValueChange, newValue: Optional(275), oldValue: Optional(-25), indexes: nil, isPrior: false)Answer:
- NO
Answer:
- Key Value Coding is a process of alternate way to access Properties of a Class.
class BankAccount: NSObject {
@objc dynamic var balance: Int = 0
func deductAnnumalMaintenance() {
balance -= 25
}
func depositAmount(amount: Int) {
balance += amount
}
func withdrawAmount(amount: Int) {
balance -= amount
}
}
class Human: NSObject {
@objc var myAccount: BankAccount = BankAccount()
var observer: NSKeyValueObservation?
func observeChangesInMyBalance() {
self.observer = self.observe(\.myAccount.balance, options: [.old, .new]) { human, change in
print(change)
}
}
deinit {
observer?.invalidate()
}
}
let human: Human = Human()
human.observeChangesInMyBalance()
human.myAccount.balance = 3000
// You can access `@objc dynamic var balance: Int` through "balance"
human.myAccount.setValue(2000, forKey: "balance")
print(human.myAccount.balance) // 2000Answer:
- dynamic says to compiler that you want to use Objective-C dynamic dispatch.
- Mainly used for KVO and for core data properties.
Answer:
- @objc indicates that the code is available for not only swift code, but also for objc code.
Section 3, Conditional Statement
Section 10, static type vs dynamic type
Section 15, higher order function
Section 21, KVO and KVC