UIResponder chain produces two extra responders-CodePudding

I'm running Xcode 14.0 beta 4. I have just one ViewController with a root view in storyboard. I want to see an entire Responder Chain from UIView to AppDelegate. To do this, I created extensions:

import UIKit

extension AppDelegate {
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        print("APPLICATION")
        next?.touchesBegan(touches, with: event)
    }
} 
extension UIView {
    public override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        print("View")
        next?.touchesBegan(touches, with: event)
    }
}
extension UIWindow {
    public override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        print("Window")
        next?.touchesBegan(touches, with: event)
    }
}

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.backgroundColor = .systemGreen
    }
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        print("CONTROLLER")
        next?.touchesBegan(touches, with: event)
    }
}

Console gives me out the following sequence:

Question:

Where do these two extra responders come from?

CodePudding user response：

These are UITransitionView and UIDropShadowView

you can either debug view hierarchy or print self to know it. There is one post on SO about it :

CodePudding user response：

I also found a way to find out what these two responders are:

class ViewController: UIViewController {

    private func responderChain(_ responder: UIResponder?) {
        if let responder {
            print(responder)
            responderChain(responder.next)
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.backgroundColor = .systemGreen

        DispatchQueue.main.async {
            self.responderChain(self)
        }
    }
}