Create a UIBarButtonItem:
UIBarButtonItem * backBarButtonItem = [[UIBarButtonItem alloc] initWithTitle: @"Back"
style: UIBarButtonItemStyleDone target: self action: @selector(onBackButtonTapped:)];
Assign it to left bar button item:
self.navigationItem.leftBarButtonItem = backBarButtonItem;
Implement onBackButtonTapped API:
- (void) onBackButtonTapped: (id) sender
{
// Display an UIAlertView
}
You may want to customize the back button. Please look into UIBarButtonItem for more details.