UIViewController's navigationController is nil

Question

I'm trying to access navigationController from UIViewController, for some reason it equals nil

AppDelegate:

self.mainViewController = [[MainViewController alloc] init];
self.navigationController = [[UINavigationController alloc] initWithRootViewController:self.mainViewController];
self.window.rootViewController = self.navigationController;

MainViewController:

 MyViewController *myViewController = [[MyViewController alloc] init];
[self.navigationController presentModalViewController:myViewController animated:YES];

Anyone has encountered this problem?

Thanks!

Are you in mainViewController and calling presentModal fine ? — Arpit B Parekh, Nov 17 '12 at 20:03
Yes, the problem is that mainViewController.navigationController is nil — jkigel, Nov 18 '12 at 06:06
Check this question might help you.http://stackoverflow.com/questions/8876212/proper-use-of-loadview-and-viewdidload-with-uiviewcontroller-without-nibs-xibs — Arpit B Parekh, Nov 18 '12 at 14:31
mainViewController.navigationController ? have you checked using NSlog for self.navigationController ? — Arpit B Parekh, Nov 18 '12 at 15:35
A navigation controller should _push_ a new view controller, not present it. It's a different method. — jrturton, Nov 18 '12 at 18:31
Yes, you should be using `pushViewController` not `presentModalViewController` which is actually deprecated now anyway. — Fogmeister, Aug 21 '13 at 16:50
Where in `MainViewController` do you instantiate `MyViewController`? It's possible that it's `navigationController` property is not yet available because you have not added `MainViewController` to a `UINavigationController` yet — Aaron, Aug 21 '13 at 16:52

score 2 · Answer 1 · answered Nov 18 '12 at 18:00

You're doing much of the correct code, but not all in the correct places. You're correct that a UINavController should be initialized with a view controller. However, in the code you sent, MainViewController's init method is complete before the nav controller is initialized.

This is due to the fact that you really shouldn't be having the MainViewController decide when to present itself. It should be initialized and presented by something outside itself - the AppDelegate, in this case.

AppDelegate:

MainViewController *mvc = [[MainViewController alloc] init];
self.navigationController = [[UINavigationController alloc] initWithRootViewController:mainViewController];
self.window.rootViewController = self.navigationController;

If you then need MainViewController to present something modally, you should do it in viewWillAppear: or viewDidLoad:, not in its init method. Alternatively, create a public method on MainViewController (showMyModal) that the app delegate can call.

Where does it say any of this code is done in the init method (genuine question, I can't see any indication of where the second code sample actually is) — jrturton, Nov 18 '12 at 18:32
The code in AppDelegate would be in whatever method you have defined that is calling the action. — tooluser, Jan 06 '13 at 20:02

score 1 · Answer 2 · answered Aug 21 '13 at 16:48

Create UINavigationController assign your viewcontroller to its root.

UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController: myViewController];
[self presentViewController:navController animated:YES completion:nil];

score 0 · Answer 3 · answered Nov 17 '12 at 20:03

0

A UIViewController may not have a UINavigationController.
The navigation controller owns some controller only if you set it expicitly:

[yourNavController setViewControllers: @[ yourViewController1, ... , yourViewControllerN] ];

answered Nov 17 '12 at 20:03

Ramy Al Zuhouri

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It is not like that initWithRootViewController is also fine. – Arpit B Parekh Nov 17 '12 at 20:05

UIViewController's navigationController is nil

3 Answers3