Question 67726 in IOS Swift Question posted in
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UIResponder chain produces two extra responders – Ios swift

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:

enter image description here

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:

enter image description here

Question:

Where do these two extra responders come from?

Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    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)
        }
    }
}

    enter image description here


  2. 0

    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 : UITransitionView and UILayoutContainerView, I don’t have much knowledge about it nor did I find any apple docs about it. They might be internal APIs

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

    enter image description here

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