Ios 如何检测容器嵌入UINavigationController何时显示新视图

我在情节提要中创建了UIViewController（A），并使用UIAVController添加了容器

我的嵌入式UINavController的根是带有按钮的UIViewController（B）

如果我点击按钮，NavController会显示一个新的UIViewController（C）

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所以我有UINavController->B->C。A-controller如何在它包含的NavController中检测B->C转换？

有很多方法可以做到这一点，但最简单的解决方案可能是使用NotificationCenter。无论何时发布通知，都要侦听通知，为其指定一个唯一的名称，如ViewA或ViewB通知，然后侦听具有该名称的通知。检查以下示例：-

import UIKit

struct NotificationNames {
    static let bViewController
    static let cViewController
}



class AViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        // Listen for notification of from BViewcontroller
        NotificationCenter.default.addObserver(self, selector: #selector(didLoadBViewController), name: Notification.Name(NotificationNames.bViewController), object: nil)

        // Listen for notification of from CViewcontroller
           NotificationCenter.default.addObserver(self, selector: #selector(didLoadCViewController), name: Notification.Name(NotificationNames.cViewController), object: nil)

    }


    @objc private func didLoadBViewController() {
        print("B ViewController is loaded.")
    }

    @objc private func didLoadCViewController() {
           print("C ViewController is loaded.")
       }

    // Remove notification listeners to save some memory
    deinit {
        NotificationCenter.default.removeObserver(self, name: NotificationNames.bViewController, object: nil)
         NotificationCenter.default.removeObserver(self, name: NotificationNames.cViewController, object: nil)
    }

}


class BViewcontroller: UIViewController {

    // Post notification that B ViewController loaded.
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(true)
        NotificationCenter.default.post(name: NotificationNames.bViewController, object: nil)
    }

}

class CViewController: UIViewController {

     // Post notification that C ViewController loaded.
    override func viewDidAppear(_ animated: Bool) {
         super.viewDidAppear(true)
        NotificationCenter.default.post(name: NotificationNames.cViewController, object: nil)
     }

}

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在UIViewController（B）中制定协议，并从UIViewController（a）中确认。然后，当您点击UIViewController（B）上的按钮时，从UIViewController（B）调用委托函数