從協議擴展調用選擇

Question

我建立簡單的主題引擎，並希望有一個擴展，它增加了UISwipeGestureRecognizer到UIViewController

這裏是我的代碼：

protocol Themeable { 
    func themeDidUpdate(currentTheme: Theme) -> Void 
} 

extension Themeable where Self: UIViewController { 
    func switchCurrentTheme() { 
     Theme.switchTheme() 
     themeDidUpdate(Theme.currentTheme) 
    } 

    func addSwitchThemeGestureRecognizer() { 
     let gestureRecognizer = UISwipeGestureRecognizer(target: self, action:#selector(Self.switchCurrentTheme)) 
     gestureRecognizer.direction = .Down 
     gestureRecognizer.numberOfTouchesRequired = 2 
     self.view.addGestureRecognizer(gestureRecognizer) 
    } 
} 

當然編譯器無法找到#selector(Self.switchCurrentTheme)因爲它沒有通過@objc指令公開。是否有可能將此行爲添加到我的擴展？

UPDATE：Theme是斯威夫特枚舉，所以我不能在前面加@objcThemeable協議

Answer 1

我不知道，但你可以像

#selector(switchCurrentTheme) 

，或者你訪問它可以參考此鏈接試試 參觀How to use #selector(myMethodName) in a protocol extension?

Answer 2

我找到了解決方案。可能不是完美的，但它的工作原理。 由於我不能將Themeable協議定義爲@objc，因爲它使用Swift-only enum我決定移動要調用「父」協議的方法並將此協議定義爲@objc。這似乎是它的工作原理，但我真的不喜歡它，說實話......

@objc protocol ThemeSwitcher { 
    func switchCurrentTheme() 
} 

protocol Themeable: ThemeSwitcher { 
    func themeDidUpdate(currentTheme: Theme) -> Void 
} 

extension Themeable where Self: UIViewController { 
    func switchCurrentTheme() { 
     Theme.switchTheme() 
     themeDidUpdate(Theme.currentTheme) 
    } 

    func addSwitchThemeGestureRecognizer() { 
     let gestureRecognizer = UISwipeGestureRecognizer(target: self, action:#selector(switchCurrentTheme)) 
     gestureRecognizer.direction = .Down 
     gestureRecognizer.numberOfTouchesRequired = 2 
     self.view.addGestureRecognizer(gestureRecognizer) 
    } 
} 

Answer 3

你有沒有考慮建立一個包裝，讓你從一個@objc打電話給你的非@ objc功能？

@objc class Wrapper: NSObject { 
    let themeable: Themeable 

    init(themeable: Themeable) { 
     self.themeable = themeable 
    } 

    func switchCurrentTheme() { 
     Theme.switchTheme() 
     themeable.themeDidUpdate(Theme.currentTheme) 
    } 
} 

protocol Themeable { 
    func themeDidUpdate(currentTheme: Theme) -> Void 
} 

extension Themeable where Self: UIViewController { 
    func addSwitchThemeGestureRecognizer() { 
     let wrapper = Wrapper(themeable: self) 
     let gestureRecognizer = UISwipeGestureRecognizer(target: wrapper, action:#selector(Wrapper.switchCurrentTheme)) 
     gestureRecognizer.direction = .Down 
     gestureRecognizer.numberOfTouchesRequired = 2 
     self.view.addGestureRecognizer(gestureRecognizer) 
    } 
} 

Answer 4

最乾淨，工作解決方案，我能想出是確定與問題的方法上UIViewController私有擴展。通過限制範圍private，訪問這個方法在協議中定義的源文件中分離到這裏是什麼樣子：

protocol Themeable { 
    func themeDidUpdate(currentTheme: Theme) -> Void 
} 

private extension UIViewController { 
    @objc func switchCurrentTheme() { 
     guard let themeableSelf = self as? Themeable else { 
      return 
     } 

     Theme.switchTheme() 
     themeableSelf.themeDidUpdate(Theme.currentTheme) 
    } 
} 

extension Themeable where Self: UIViewController { 
    func addSwitchThemeGestureRecognizer() { 
     let gestureRecognizer = UISwipeGestureRecognizer(target: self, action:#selector(switchCurrentTheme)) 
     gestureRecognizer.direction = .Down 
     gestureRecognizer.numberOfTouchesRequired = 2 
     self.view.addGestureRecognizer(gestureRecognizer) 
    } 
}