如何为子类覆盖快速协议功能（例如，UIView中的UILabel）

您可以通过以下方式实现，您只需在中将其方法公开aProtocol给Objective-c运行时即可。overridingextension

@objc protocol aProtocol {
    typealias completiOnBlock= (_ finished:Bool)->()
    func doSomething(completion: completionBlock)
}

extension UIView: aProtocol {
    func doSomething(completion: (Bool) -> ()) {
        print("Im an UIView")
    }
}

extension UILabel {
    override func doSomething(completion: (Bool) -> ()) {
        // you can call super.doSomething(completion: completion)
        print("im an UILabel")
    }
}

extension UIImageView {
    override func doSomething(completion: (Bool) -> ()) {
        // you can call super.doSomething(completion: completion)
        print("im an UIImageView")
    }
}

输出：

Im an UIView
Im an UIView
im an UILabel
im an UIImageView