Setting the back button title of a UINavigationItem

The following code will set the back button title of the current UINavigationItem:

Updated to fix memory leak. (Thanks Sam!)

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UIBarButtonItem *backButton = [[UIBarButtonItem alloc]
    initWithTitle:@"Back"
            style:UIBarButtonItemStylePlain
           target:nil
           action:nil];
[self.navigationItem setBackBarButtonItem:backButton];
[backButton release];

The target: and action: parameters are definitely ignored (replaced by the default back button behavior) and the style also seems to be ignored because the back button retains its pointed left side.

This next block of code looks like it should do the same thing but does not work:

~~self.navigationItem.backBarButtonItem.title = @"Back";~~

This is because the back button is “owned” by the previous view on the stack (as pointed out in this thread). In other words, the setBackBarButtonItem method should be called on the view that the user is navigating away from, rather than the view above which this button is actually displayed.

UINavigationItem on Apple Developer Docs

UIBarButtonItem *backButton = [[UIBarButtonItem alloc] initWithTitle:@"Back" style:UIBarButtonItemStylePlain target:nil action:nil]; [self.navigationItem setBackBarButtonItem:backButton]; [backButton release];

UIBarButtonItem* newBarButtonItem = [[[UIBarButtonItem alloc] initWithTitle:@"Map" style:UIBarButtonItemStylePlain target:nil action:nil] autorelease]; [theMapViewController.navigationItem setBackBarButtonItem:newBarButtonItem];

Comments

shoaib on 3 Apr 2009 at 2:52 am

Hi, By adding the above code, Back button is enabled but it shows memory leakage. Is there any way to avoid memory leakage?

George on 15 Apr 2009 at 9:48 am

Thank you for this! I was banging my head against the wall on this one - the Apple developer site only hints at what needs to be done.

George on 15 Apr 2009 at 9:56 am

PS to Shoaib, try looking at where you have placed the back button code. As Adam mentioned, it should go in the view that the user is navigating away from, rather than in the view that the user is navigating to. It seems to work wherever you put the code, but I think it should go right before your: [self.navigationController pushViewController:newViewName animated:YES]; statement.

Sam Soffes on 13 Jul 2009 at 7:52 pm

That would create a leak. Do this instead:

Duncan Champney on 9 Jan 2010 at 2:36 am

@shoaib, The memory leakage is because the UIBarButtonItem is being created with a retain count of 1. It should be autoreleased before adding it to the navigation item, like this: (split into 2 lines for clarity)
UIBarButtonItem* newBarButtonItem = [[[UIBarButtonItem alloc] initWithTitle:@"Map" style:UIBarButtonItemStylePlain target:nil action:nil] autorelease];
[theMapViewController.navigationItem setBackBarButtonItem:newBarButtonItem];