swift - 在协议(protocol)扩展中覆盖 touchesBegan

Question

我正在尝试创建一个协议(protocol)，这样我就可以让我的一些按钮符合这个协议(protocol)，并在调用 touchesBegan 时播放声音。

协议(protocol)看起来像这样:

protocol AddSound: class {
    func addSound()
}

extension AddSound where Self: UIButton {
    func addSound() { print("play some sound") }
}

class CustomButton: UIButton, AddSound {

    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesBegan(touches, with: event)

        addSound()
    }
}

这可行，但这意味着我每次使用协议(protocol) AddSound 时都必须手动覆盖 touchesBegan。

是否有可能在 AddSound 的扩展中覆盖 touchesBegan 或者甚至是 UIButton 本身的扩展，符合协议(protocol) 添加声音?

这行不通:

extension AddSound where Self: UIButton {
    func addSound() { print("playing some sound") }

    // can't override touchesBegan
    func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        self.touchesBegan(touches, with: event)

        addSound()
    }
}

Answer 1

方式一

protocol AddSound: class {
    func addSound()
}

extension UIButton: AddSound {
    func addSound() { print("play some sound") }

    override open func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesBegan(touches, with: event)
        addSound()
        print("touchesBegan")
    }
}

用法

class ViewController: UIViewController {

    var button = UIButton(frame: CGRect(x: 40, y: 40, width: 80, height: 40))

    override func viewDidLoad() {
        super.viewDidLoad()
        button.setTitle("Button", for: .normal)
        button.setTitleColor(UIColor.blue, for: .normal)
        view.addSubview(button)
    }
}

方式二

protocol AddSound: class {
    func addSound()
}

class MyButton: UIButton, AddSound {
    func addSound() { print("play some sound") }

    override open func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesBegan(touches, with: event)
        addSound()
        print("touchesBegan")
    }
}

用法

....
var button = MyButton(frame: CGRect(x: 40, y: 40, width: 80, height: 40))
....

结果

点击按钮，你会看到: