iPhone Objective-C: Programmatically change title of tab bar item in tab bar created using IB?

[[self.parentViewController.tabBarController.tabBar.items objectAtIndex:2] title] = @"string";

The syntax is slightly off here. You probably wanted something like:

[[self.parentViewController.tabBarController.tabBar.items objectAtIndex:2].title = @"string";

However, that won't work, since there is no title property to set. In fact, there's no way I can see to change a UITabBarItem's title once it's been initialized. You'll have to use UITabBar's setItems:animated: method to set the entire group of items at once. But it won't be fun.

I bet this would be an Apple HIG violation, which is why there's no easy way to do it with the current API. Rethink your design and ask yourself why you want to change the names of the tabs, which will confuse your users.

Try setting the title in awakeFromNib instead of viewDidLoad. The view for a view controller is not actually loaded until you need the view, and the tab bar controller by default doesn't access the view of a view controller until you actually select it (which is why you saw the title change when you selected the tab).

Since the nib is creating the view controller to start with (assuming you have built your tab bar controller in IB) awakeFromNib will be called as soon as the view controller has been built, before the tab bar controller can ask what the title is.