Triggering an event when user clicks "< Back" button

Question

I have fairly simple UINavigationControllers with two screens: screen1 & screen2.

When the user is on screen2 and clicks < Back I want to trigger an event before screen1 is shown -- basically I want to fetch data from the server for screen1.

Is there a way to do this?

Answer 1

In your viewDidLoad do this:

UIBarButtonItem *backBarButton = [[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:@"icon_back.png"] style:UIBarButtonItemStylePlain target:self action:@selector(goBack:)];
self.navigationItem.leftBarButtonItem = backBarButton;

Implement the method goBack:

- (void)goBack:(id)sender {
    //Do something
    [self.navigationController popViewControllerAnimated:YES];
}

Hope this helps.. :)