从协议扩展调用选择

Question

我建立简单的主题引擎，并希望有一个扩展，它增加了UISwipeGestureRecognizer到UIViewController

这里是我的代码：

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) 
    } 
} 

当然编译器无法找到#selector(Self.switchCurrentTheme)因为它没有通过@objc指令公开。是否有可能将此行为添加到我的扩展？

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

Answer 1

我不知道，但你可以像

#selector(switchCurrentTheme) 

，或者你访问它可以参考此链接试试 参观How to use #selector(myMethodName) in a protocol extension?

Answer 2

我找到了解决方案。可能不是完美的，但它的工作原理。 由于我不能将Themeable协议定义为@objc，因为它使用Swift-only enum我决定移动要调用“父”协议的方法并将此协议定义为@objc。这似乎是它的工作原理，但我真的不喜欢它，说实话......

@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

你有没有考虑建立一个包装，让你从一个@objc打电话给你的非@ 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

最干净，工作解决方案，我能想出是确定与问题的方法上UIViewController私有扩展。通过限制范围private，访问这个方法在协议中定义的源文件中分离到这里是什么样子：

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) 
    } 
}