self.navigationItem available in any class?

Question

If a viewController is in a navigationStack(probably top of stack),
does it automatically possess self.navigationItem?

I keep seeing self.navigationItem and self.navigationController without much context in questions and tutorials, and wonder where that variables are set.

edit

Wow thanks for the fast answers.
Where would I have spotted the info(about self.navigationItem) in the official doc?

score 1 · Accepted Answer · answered Jun 28 '12 at 07:31

1

Yes if its in a stack it does have a self.navigationItem, if its not in a navigation stack self.navigationItem would equal to nil

This property is defined in an objective c class extension

@interface UIViewController (UINavigationControllerItem)

it defines the properties of UIViewController related to the navigation controller

answered Jun 28 '12 at 07:31

Omar Abdelhafith

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Thanks, where in the doc says so? Is this a relatively new addition to the iOS library?(5.0+?) – eugene Jun 28 '12 at 07:40
No actually its not a new addition, its prior to 4 i guess am not sure its defined in UINavigationController.h – Omar Abdelhafith Jun 28 '12 at 07:42

score 0 · Answer 2 · answered Jun 28 '12 at 07:33

Yes, you will see the self.navigationItem and self.navigationController properties set in every controller that is added to the stack of navigation controller. These properties get set once you call pushViewController:animated or initWithRootViewController:.

score 0 · Answer 3 · answered Jun 28 '12 at 07:33

They are not set by you, unless you specifically tell it. There are others properties that are not assigned by you directly as well, for example:

self.tabBarController;

self.parentViewController;

That's why you should check if it is nil, before trying to access a property.

self.navigationItem available in any class?

3 Answers3