ios - 仅当符合协议(protocol)时才扩展 UIButton

Question

我正在尝试为 UIButton 创建多个扩展，这样我只需向自定义按钮添加协议(protocol)即可轻松添加一些功能。如果我不必重写 UIButton 中的某些方法，那就容易多了，所以我想我必须为 UIButton 本身进行扩展。

例如，我的自定义按钮可以遵循多个协议(protocol):

protocol CustomLayer { }

protocol ButtonSound { }

到目前为止，我只设法为 UIButton 创建一个扩展，没有任何限制(这些是简化版本):

// Only when the button conforms to protocol CustomLayer
extension UIButton {
    override public class func layerClass() -> AnyClass { return CAShapeLayer.self }
}

// Only when the button conforms to protocol ButtonSound
extension UIButton {
    override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
        super.touchesBegan(touches, withEvent: event)

        AudioServicesPlaySystemSound(1104)
    }
}

我读过一些帖子，我可以使用 UIButton 类的 where 子句为协议(protocol)本身进行扩展:

extension CustomLayer where Self: UIButton { }

但是我无法重写 UIButton 本身的任何方法。

其他建议(例如子类化)有效，但某些按钮不能具有相同的功能:

class A: CustomLayer { } // Can't have ButtonSound, single subclass works
class B: ButtonSound { } // Can't have CustomLayer, single subclass works

class C: CustomLayer, ButtonSound { } // Error: multiple inheritance from classes

Answer 1

import Foundation

protocol BackButtonDelegate {

    func BackButtonAction(sender:UIButton)
}

class NavigationBack: UIButton
{
     var delegate : BackButtonDelegate!

    override func drawRect(rect: CGRect) {
        self.frame = CGRectMake(0, 0, 60, 60)
        self.setTitle("Back", forState: .Normal)
        self.titleLabel?.font = UIFont(name: "Helvetica",size: 12)
        self.setImage(UIImage(named: "back-arrow"), forState: .Normal)

        self.addTarget(self, action: #selector(NavigationBack.click(_:)), forControlEvents: UIControlEvents.TouchUpInside)

   }
    func click(sender:UIButton)
    {
        if delegate != nil
        {
            delegate!.BackButtonAction(sender)
        }
    }

}