Swift：如何在回调闭包中使用instanceType

我想将self作为instancetype传递给此函数的回调闭包：

extension UIView {
    public func onTap(_ handler: @escaping (_ gesture: UITapGestureRecognizer, _ view: Self) -> Void) -> UITapGestureRecognizer {
        ...
    }
}

let view = UIView.init()
view.onTap { tap, v in
    ...
}

但我有一个错误：

Self' is only available in a protocol or as the result of a method in a class; did you mean 'UIView'?

---

如何做到这一点？

如果您可以在Swift中非常有效地使用协议和扩展，这正是书本上的完美场景：

protocol Tappable { }

extension Tappable { // or alternatively: extension Tappable where Self: UIView {
    func onTap(_ handler: @escaping (UITapGestureRecognizer, Self) -> Void) -> UITapGestureRecognizer {
        return UITapGestureRecognizer() // as default to make this snippet sane
    }
}

extension UIView: Tappable { }

然后，例如：

let button = UIButton.init()
button.onTap { tap, v in
    // v is UIButton...
}

let label = UILabel.init()
label.onTap { tap, v in
    // v is UILabel...
}

而对于例如：

let button = UIButton.init()
button.onTap { tap, v in
    // v is UIButton...
}

let label = UILabel.init()
label.onTap { tap, v in
    // v is UILabel...
}

等等

注意：您可以在Apple的中阅读更多关于或的信息