Action to Navigation bar back button

Question

I want to show an alert with Confirmation when user clicks on back button. This is how I\'m trying to add action.

self.navigationItem.hidesBackButton = true
         


        

Answer 1

Call this line of code inside of your ParentViewController's viewDidLoad method not the ChildViewController

self.navigationItem.backBarButtonItem = UIBarButtonItem(title: "", style: .plain, target: nil, action: nil)

Remove the following line of code from your ChildViewController

self.navigationItem.hidesBackButton = true

And you'll be Ok! If you need to create an action for this transition, I mean whenever the user taps the back button from your ChildViewController. Simply call this method inside of your ChildViewController

 override func didMove(toParentViewController parent: UIViewController?) {
    super.didMove(toParentViewController: parent)

    if parent == nil {

    } else {

    }
}

Edited:

ChildViewController

 override func didMove(toParentViewController parent: UIViewController?) {
    super.didMove(toParentViewController: parent)

    if parent == nil {
        NotificationCenter.default.post(name: NSNotification.Name.init("Post"), object: nil)
    } else {

    }

}

ParentViewController

 override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

    NotificationCenter.default.addObserver(self, selector: #selector(self.handler(notification:)), name: NSNotification.Name.init(rawValue: "Post"), object: nil)

}

func handler(notification: Notification) {

    let alertController = UIAlertController(title: "Hello", message: nil, preferredStyle: .alert)
    alertController.addAction(UIAlertAction(title: "Dismiss", style: .default, handler: nil))
    self.present(alertController, animated: true, completion: nil)

}

This is works but with a problem like so:

Warning: Attempt to present on while a presentation is in progress!

Therefore I don't recommended. Good luck