检测视图控制器何时从pop出现

class MyViewController: UIViewController, UINavigationControllerDelegate {
    override func viewDidLoad() {
        super.viewDidLoad()
        navigationController?.delegate = self
    }
    
    func navigationController(_ navigationController: UINavigationController, didShow viewController: UIViewController, animated: Bool) {
        if let poppedViewController = navigationController.transitionCoordinator?.viewController(forKey: .from),
           !navigationController.viewControllers.contains(poppedViewController) {
            // 视图控制器已经从导航堆栈中弹出
            // 在这里执行相应的操作
        }
    }
}

class MyViewController: UIViewController {
    private var observation: NSKeyValueObservation?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        observation = navigationController?.observe(\.viewControllers, options: [.old, .new], changeHandler: { [weak self] (_, change) in
            guard let oldViewControllers = change.oldValue, let newViewControllers = change.newValue else {
                return
            }
            
            if oldViewControllers.count > newViewControllers.count {
                // 视图控制器已经从导航堆栈中弹出
                // 在这里执行相应的操作
            }
        })
    }
    
    deinit {
        observation?.invalidate()
    }
}