Swift3扩展"Any？" - 班级？

更简短的解释:

你经常想要扩展"目标"......通常是目标Any?.但你不能扩展Any.怎么做？

想想这个,

extension UIViewController {    
    func add(tap v:UIView, _ action:Selector) {
        let t = UITapGestureRecognizer(target: self, action: action)
        v.addGestureRecognizer(t)
    }
}

很好,你现在可以......

self.tap(redButton, #selector(clickedRedButton))

...在任何视图控制器中.

但你可以对任何目标做同样的事情.

所以,要在UITableViewCell上使用扩展说,你还必须拥有....

extension UIGestureRecognizerDelegate {
        func add(tap v:UIView, _ action:Selector) {
        let t = UITapGestureRecognizer(target: self, action: action)
        v.addGestureRecognizer(t)
    }
}

UITapGestureRecognizer的目标参数实际上是 Any?

但是,你不能这样做......

extension Any { 

解决方案是什么？如何制作一个可以在其上工作的扩展,Any?例如在第一个参数中UITapGestureRecognizer？

或者正如Conner'c评论所暗示的,有没有办法:

extension  UIViewController or UIView {

而不是复制和粘贴两次？

每个结构/类都遵循"被动"的"任何".Any的扩展会将该功能添加到语言和代码中的每个类型.目前这是不可能的,我怀疑它是否(或应该是).

无论如何,这里有几种方法可以解决这个问题.

我的首选是添加功能的协议扩展:

protocol TapGestureAddable {
    func addTapGestureRecognizer(to view: UIView, with action: Selector) -> UITapGestureRecognizer
}

extension TapGestureAddable {
    func addTapGestureRecognizer(to view: UIView, with action: Selector) -> UITapGestureRecognizer {
        let recognizer = UITapGestureRecognizer(target: self, action: action)
        view.addGestureRecognizer(recognizer)
        return recognizer
    }
}

extension UIViewController: TapGestureAddable { }
extension UIView: TapGestureAddable { }

这迫使你有意识地选择将功能添加到给定的类(IMO),而不必复制任何有意义的代码.

可能更好的选择是使这个逻辑成为UIView的扩展:

extension UIView {

    func addTapGestureRecognizer(with responder: Any, for action: Selector)  -> UITapGestureRecognizer {
        let recognizer = UITapGestureRecognizer(target: responder, action: action)
        self.addGestureRecognizer(recognizer)
        return recognizer
    }

    func addTapGestureRecognizer(with action: Selector)  -> UITapGestureRecognizer {
        let recognizer = UITapGestureRecognizer(target: self, action: action)
        self.addGestureRecognizer(recognizer)
        return recognizer
    }
}

否则,只需创建一个全局函数:

func addTapGestureRecognizer(to view: UIView, with responder: Any, for action: Selector) -> UITapGestureRecognizer {
    let recognizer = UITapGestureRecognizer(target: responder, action: action)
    view.addGestureRecognizer(recognizer)
    return recognizer
}