Execute action when back bar button of UINavigatio

Question

I need to execute an action (emptying an array), when the back button of a UINavigationController is pressed, while the button still causes the previous ViewController on the stack to appear. How could I accomplish this using swift?

Answer 1

As I understand you want to empty your array as you press your back button and pop to your previous ViewController let your Array which you loaded on this screen is

let settingArray  = NSMutableArray()
@IBAction func Back(sender: AnyObject) {
    self. settingArray.removeAllObjects()
    self.dismissViewControllerAnimated(true, completion: nil)
} 

Answer 2

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.isMovingFromParent {
        // Your code...
    }
}

Answer 3

Try this .

self.navigationItem.leftBarButtonItem?.target = "methodname"
func methodname ( ) {            
  //    enter code here
}

Try on this too.

override func viewWillAppear(animated: Bool) {
  //empty your array
}

Answer 4

override func willMove(toParentViewController parent: UIViewController?)
{
    super.willMove(toParentViewController: parent)
    if parent == nil
    {
        print("This VC is 'will' be popped. i.e. the back button was pressed.")
    }
}

Answer 5

If you are using navigationController then add the UINavigationControllerDelegate protocol to class and add the delegate method as follows:

class ViewController:UINavigationControllerDelegate {

    func navigationController(navigationController: UINavigationController, willShowViewController viewController: UIViewController,
animated: Bool) {
        if viewController === self {
            // do here what you want
        }
    }
}

This method is called whenever the navigation controller will slide to a new screen. If the back button was pressed, the new view controller is ViewController itself.

Answer 6

It's not difficult as we thing. Just create a frame for UIButton with clear background color, assign action for the button and place over the navigationbar back button. And finally remove the button after use.

Here is the Swift 3 sample code done with UIImage instead of UIButton

override func viewDidLoad() {
    super.viewDidLoad()
    let imageView = UIImageView()
    imageView.backgroundColor = UIColor.clear
    imageView.frame = CGRect(x:0,y:0,width:2*(self.navigationController?.navigationBar.bounds.height)!,height:(self.navigationController?.navigationBar.bounds.height)!)
    let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(back(sender:)))
    imageView.isUserInteractionEnabled = true
    imageView.addGestureRecognizer(tapGestureRecognizer)
    imageView.tag = 1
    self.navigationController?.navigationBar.addSubview(imageView)
    }

write the code need to be executed

func back(sender: UIBarButtonItem) {

    // Perform your custom actions}
    _ = self.navigationController?.popViewController(animated: true)

    }

Remove the subView after action is performed

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

    for view in (self.navigationController?.navigationBar.subviews)!{
        if view.tag == 1 {
            view.removeFromSuperview()
        }
    }