NSNotification does not reach all Observers

I use NSNotification for a particular set of events. I have three views such that I have an "ADD" button on view 1 and clicking that makes me navigate from view 1 to view 2 to view 3 and again back to view 1.

1->2->3->1

I use NSNotifications to push a view controller if the ADD button on view 1 is clicked, and I update the other views respectively, based on the notification posted by View 1.

When the notification is sent from view 1, only view 2 receives it. View 3 does not.

How is this possible? The code for observers is EXACTLY the same on view 2 and view 3.

This is the code for adding observers in view 2 and view 3:

[[NSNotificationCenter defaultCenter] addObserver:self 
                        开发者_StackOverflow社区                 selector:@selector(didPressAdd:) 
                                             name:@"DidAddNotification" 
                                           object:nil];

I also remove them in the dealloc() function properly.

Navigating back to 1 using navigation controller will remove 2 and 3. So in dealloc, add a log saying that the particular controller has stopped listening. You shall see that the listener is being deallocated after which it won't listen to notifications. Updated the sample to send a notification on return.

It's because viewDidLoad and viewWillAppear: are called after you send the notification. Set it up in initWithNibName:bundle: instead (if you use xib files) or some other init method if you don't (initWithCoder: for example), assuming you have inited the controller somewhere. If you have not inited the controller, you can't really listen for notifications inside it either.