Execute Action When Back Bar Button of Uinavigationcontroller Is Pressed

Execute action when back bar button of UINavigationController is pressed

One option would be implementing your own custom back button. You would need to add the following code to your viewDidLoad method:

- (void) viewDidLoad {
    [super viewDidLoad];
    self.navigationItem.hidesBackButton = YES;
    UIBarButtonItem *newBackButton = [[UIBarButtonItem alloc] initWithTitle:@"Back" style:UIBarButtonItemStyleBordered target:self action:@selector(back:)];
    self.navigationItem.leftBarButtonItem = newBackButton;
}

- (void) back:(UIBarButtonItem *)sender {
    // Perform your custom actions
    // ...
    // Go back to the previous ViewController
    [self.navigationController popViewControllerAnimated:YES];
}

UPDATE:

Here is the version for Swift:

    override func viewDidLoad {
        super.viewDidLoad()
        self.navigationItem.hidesBackButton = true
        let newBackButton = UIBarButtonItem(title: "Back", style: UIBarButtonItemStyle.Bordered, target: self, action: "back:")
        self.navigationItem.leftBarButtonItem = newBackButton
    }

    func back(sender: UIBarButtonItem) {
        // Perform your custom actions
        // ...
        // Go back to the previous ViewController
        self.navigationController?.popViewControllerAnimated(true)
    }

UPDATE 2:

Here is the version for Swift 3:

    override func viewDidLoad {
        super.viewDidLoad()
        self.navigationItem.hidesBackButton = true
        let newBackButton = UIBarButtonItem(title: "Back", style: UIBarButtonItemStyle.plain, target: self, action: #selector(YourViewController.back(sender:)))
        self.navigationItem.leftBarButtonItem = newBackButton
    }

    func back(sender: UIBarButtonItem) {
        // Perform your custom actions
        // ...
        // Go back to the previous ViewController
        _ = navigationController?.popViewController(animated: true)
    }

Detect if default back button in navigation bar is pressed

In your viewWillDisappear method, add the isMovingFromParentViewController property:

if self.isMovingFromParentViewController {
    //do stuff, the back button was pressed
}

EDIT: As had pointed out, if you are merely dismissing the view controller when the save button is pressed, you need a Bool value to check if the save button was pressed or the default back button.

At the top of your class, define a Boolean value:

var saveButtonPressed = false

I'm assuming that you have an @IBAction method linked to your save button. If you don't, then I suggest you add that connection.

In that method, set saveButtonPressed equal to true.

Then, in your viewWillDisappear method, add this to the if condition:

if (self.isMovingFromParentViewController && !saveButtonPressed) {
    //do stuff, the back button was pressed
}

Trying to handle back navigation button action in iOS

Try this code using VIewWillDisappear method to detect the press of The back button of NavigationItem:

-(void) viewWillDisappear:(BOOL)animated
{
    if ([self.navigationController.viewControllers indexOfObject:self]==NSNotFound) 
    {
        // Navigation button was pressed. Do some stuff 
        [self.navigationController popViewControllerAnimated:NO];
    }
    [super viewWillDisappear:animated];
}

OR There is another way to get Action of the Navigation BAck button.

Create Custom button for UINavigationItem of back button .

For Ex:

In ViewDidLoad :

- (void)viewDidLoad 
{
    [super viewDidLoad];
    UIBarButtonItem *newBackButton = [[UIBarButtonItem alloc] initWithTitle:@"Home" style:UIBarButtonItemStyleBordered target:self action:@selector(home:)];
    self.navigationItem.leftBarButtonItem=newBackButton;
}

-(void)home:(UIBarButtonItem *)sender 
{
    [self.navigationController popToRootViewControllerAnimated:YES];
}

Swift :

override func willMoveToParentViewController(parent: UIViewController?) 
{
    if parent == nil 
    {
        // Back btn Event handler
    }
}

Go back to root when nav back button is press

Personally I would not recommend what you are trying to achieve, but anyways here is a different solution without customizing the back button.

Steps to implement

1. Create CustomNavigationController by subclassing
   UINavigationController
2. Override popViewController(animated:)
3. When ViewController conforms to Navigationable and
   
   
   • shouldCustomNavigationControllerPopToRoot() returns true, call super.popToRootViewController
   • Otherwise proceed with normally popping the ViewController

Source Code

Custom Navigation Controller

import UIKit

class CustomNavigationController: UINavigationController {

    // MARK: - Initializers

    override init(rootViewController: UIViewController) {
        super.init(rootViewController: rootViewController)

        initialSetup()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)

        initialSetup()
    }

    // MARK: - Setups

    private func initialSetup() {
        // DISCLAIMER: This code does not support `interactivePopGestureRecognizer`, therefore we disable it
        interactivePopGestureRecognizer?.delegate = nil
    }

    // MARK: - Overrides

    override func popViewController(animated: Bool) -> UIViewController? {
        if shouldNavigationPopToRoot {
            return super.popToRootViewController(animated: animated)?.last
        }

        return super.popViewController(animated: animated)
    }

    // MARK: - Helpers

    private var shouldNavigationPopToRoot: Bool {
        return (topViewController as? Navigationable)?.shouldCustomNavigationControllerPopToRoot() == true
    }
}

View Controller conforming to Navigationable

import UIKit

protocol Navigationable: class {
    func shouldCustomNavigationControllerPopToRoot() -> Bool
}

class ViewController: UIViewController, Navigationable {

    // MARK: - Protocol Conformance
    // MARK: Navigationable

    func shouldCustomNavigationControllerPopToRoot() -> Bool {
        return true
    }
}

Output

UINavigationController and back button action

Or you can use the UINavigationController's delegate methods. The method willShowViewController is called when the back button of your VC is pressed.

- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated;

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