After pushViewController, how to disable the backBarButtonItem?

After pushViewController, how to disable the backBarButtonItem, that going back开发者_StackOverflow will not be possible?

navigationItem.hidesBackButton = YES

if you use a storyboard, click Navigation Item and add "hidesBackButton" path into the Key Path Attributes tag.

I ran into this issue and used following to hide the nav bar:

[self.navigationController setNavigationBarHidden: YES animated:YES];