在協議

Question

使用方法，我創建了一個協議，該協議的擴展：

protocol SomeProtocol: class { 
    var someView: UIView { get set } 

    func handlePan(recognizer: UIPanGestureRecognizer) 
} 

extension SomeProtocol where Self: UIViewController { 
    func handlePan(recognizer: UIPanGestureRecognizer) { 
     // implementation 
    } 
} 

class SomeViewController: UIViewController, SomeProtocol { 

    var someView = UIView() 

    override func viewDidLoad() { 
     super.viewDidLoad() 

     someView.frame = CGRect(x: 100, y: 200, width: 50, height: 50) 
     someView.addGestureRecognizer(UIPanGestureRecognizer(target: self, action: #selector(handlePan))) 
     someView.backgroundColor = .black 

     view.addSubview(someView) 
    } 
} 

但是，這是給我的錯誤的IM創造UIPanGestureRecognizer：

Error: Argument of '#selector' refers to instance method 'handlePan(recogniser:)' that is not exposed to Objective-C

是否有方法來解決這個問題，而不是在視圖控制器中添加handlePan方法？

Answer 1

您需要@objc來註釋協議將其暴露在Objective-C的運行時庫：

@objc protocol SomeProtocol: class { //...