Optional Methods in Swift Protocol

* This makes empty implementations unnecessary
* Note that method calls have changed too

Author: yakovmanshin

BirdProcessor/UI/ViewController.m

@@ -28,15 +28,7 @@ - (IBAction)didTapProcessButton:(UIButton *)sender {
     [self.resultLabel setText:processingResult];
 }
 
-// We’re only interested in the third method, but the compiler requires all three:
-
-- (void)wordProcessor:(WordProcessor *)processor didBeginProcessingInput:(NSString *)string {
-    
-}
-
-- (void)wordProcessor:(WordProcessor *)processor didFinishProcessingInput:(NSString *)string {
-    
-}
+// We can implement only the method that we actually need:
 
 - (void)wordProcessor:(WordProcessor *)processor didEncounterError:(NSString *)error {
     // Show an error alert

BirdProcessor/WordProcessor/WordProcessor.swift

@@ -10,11 +10,11 @@
     }
 
     @objc func processInputString(_ string: String) -> String {
-        delegate?.wordProcessor(self, didBeginProcessingInput: string)
+        delegate?.wordProcessor?(self, didBeginProcessingInput: string)
         // This runs *after* the resulting string is constructed
         // but *before* control is returned to the caller—
         // in other words, when processing is truly finished
-        defer { delegate?.wordProcessor(self, didFinishProcessingInput: string) }
+        defer { delegate?.wordProcessor?(self, didFinishProcessingInput: string) }
 
         let isEmpty = stringManipulator.isEmpty(string)
         let isEmptyResult = isEmpty ? "is" : "is not"
@@ -25,7 +25,7 @@
         } else { "" }
 
         if numberOfWordsResult.isEmpty {
-            delegate?.wordProcessor(self, didEncounterError: "Cannot count words")
+            delegate?.wordProcessor?(self, didEncounterError: "Cannot count words")
         }
 
         let numberOfCharacters = stringManipulator.numberOfCharacters(in: string)

BirdProcessor/WordProcessor/WordProcessorDelegate.swift

@@ -1,5 +1,5 @@
 @objc protocol WordProcessorDelegate {
-    func wordProcessor(_ processor: WordProcessor, didBeginProcessingInput string: String)
-    func wordProcessor(_ processor: WordProcessor, didFinishProcessingInput string: String)
-    func wordProcessor(_ processor: WordProcessor, didEncounterError error: String)
+    @objc optional func wordProcessor(_ processor: WordProcessor, didBeginProcessingInput string: String)
+    @objc optional func wordProcessor(_ processor: WordProcessor, didFinishProcessingInput string: String)
+    @objc optional func wordProcessor(_ processor: WordProcessor, didEncounterError error: String)
 }

README.md

@@ -10,4 +10,4 @@ You’ll find different stages of the project in separate branches.
 * [x] Fix the crash that occurs when the non-implemented optional method is called
 * [x] Replace `WordProcessor` with a Swift version and use the better way to handle the optional method
 * [x] Declare the `WordProcessorDelegate` protocol in Swift and implement it in Objective-C (`ViewController`)
-* [ ] Mark the protocol’s methods as `optional` and remove the unneeded method implementations
+* [x] Mark the protocol’s methods as `optional` and remove the unneeded method implementations