Merge pull request #7 from coffmark/feature/update-readme

Update README.md

README.md

@@ -1,16 +1,36 @@
 # `@AccessAssociatedValue` Macros
 
+<img src="./images/usage.png" >
+
+If you expand macros, it'll look like this
 ```swift
 @AccessAssociatedValue
 enum ViewState {
   case loading(isInticator: Bool)
   case success(cards: [String], isIndicator: Bool)
   case failed(isIndicator: Bool)
-}
 
-let viewState = ViewState.success(cards: ["Card1", "Card2"], isIndicator: false)
-print(viewState.loading) // nil
-print(viewState.success?.cards) // ["Card1", "Card2"]
++ var loading: (isIndicator: Bool)? {
++   guard case let .loading(isIndicator) = self else {
++     return nil
++  }
++   return (isIndicator)
++ }
++
++ var success: (cards: [String], isIndicator: Bool)? {
++   guard case let .success(cards, isIndicator) = self else {
++     return nil
++   }
++   return (cards: cards, isIndicator: isIndicator)
++ }
++
++ var failed: (isIndicator: Bool)? {
++   guard case let .failed(isIndicator) = self else {
++     return nil
++   }
++   return (isIndicator)
++ }
+}
 ```
 - Easy to access associated value
 - Type safe