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I would like to perform some actions when a user presses the "Back" button on my Navigation Controller. Is there a Swift function that is called when this happens?

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GED125
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5 Answers5

5

Try this (copied and pasted from manecosta)

Replacing the button to a custom one as suggested on another answer is possibly not a great idea as you will lose the default behavior and style.

One other option you have is to implement the viewWillDisappear method on the View Controller and check for a property named isMovingFromParentViewController. If that property is true, it means the View Controller is disappearing because it's being removed (popped).

Should look something like:

override func viewWillDisappear(animated : Bool) {
    super.viewWillDisappear(animated)

    if (self.isMovingFromParentViewController()){
        // Your code...
    }
}

Here is the link to the other question

Community
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Dan Levy
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4

Try to call this 

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

    if self.isMovingFromParent {
        print("isMovingFromParent()") // dismiss for push viewController
    }
    if self.isBeingDismissed {
        print("isBeingDismissed()") // dismiss for modal that doesn't has navigationController
    }
    if self.navigationController?.isBeingDismissed ?? false {
        print("navigationController?.isBeingDismissed()") // dismiss for modal that has navigationController
    }
}
Supanat Techasothon
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3
override func viewWillDisappear(animated: Bool) {
// Do Your Lines of Code ... 
}

Everytime when back button or Done is pressed or a view is popped out this function is called.. you need to override this..

Abdul Waheed
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    Keep in mind using this will also be called if the viewController presents or pushes another viewController. – Slayter Apr 08 '16 at 18:24
2

Try this:

override func willMoveToParentViewController(parent: UIViewController?) {
    if parent == nil {
        // Back button Event handler
    }
}
Twitter khuong291
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  • I tested this and the weird thing is that this function is called before I get to the view controller, as well as when I click the back button. Unfortunately that will not work for me. Adbul's function is called when I need it to be. – GED125 Apr 08 '16 at 17:59
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    Abdul's function sometime will got some error if the current ViewController continue to push to another ViewController. – Twitter khuong291 Apr 08 '16 at 18:03
  • This method is not getting called at all – zulkarnain shah May 23 '17 at 09:03
  • The function name is changed in Swift 4 (or 3) to `willMove(toParentViewController:)`. If this method doesn't get called, is your viewController inside `UINavigationController`? Does it has own back-button instead of the one supplied by `UINavigationController`? – John Pang Sep 13 '18 at 17:03
1

Swift 5

"viewWillDisappear" call Every time for forward or backward. But if you add this check it's call only when back from controller.

override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
       
        if self.isMovingFromParent {
            print("Only back action")
        }
    }
Sahidul Islam
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