Where should I remove a notification observer?

Question

I set up a notification observer in my view controller's init method like so:

[[NSNotificationCenter defaultCenter] 
                    addObserver:self
                    selector:@selector(saveState)
                    name:UIApplicationWillResignActiveNotification
                    object:nil];

Where is the best place to call removeObserver:name:object: for this notification. I'm currently calling it in my dealloc method, but wanted to know if that might cause problems.

Schistosome

Answer 1

No, you got it right. dealloc is the correct location to remove notification observers (unless you have some specific reason to need to remove the observer earlier).

Linger

Thanks for this, nice to get confirmation. – Schistosome

Could you please post a reference to the official documentation. – Uncanonical

Answer 2

You can always remove the observer in viewWillDisappear:, or when you are done using it and have no other need for it, you can place it in a function.

Joceline

Unless the view is going to appear again. I think your approach would work if I started the notification observer in viewWillAppear:. – Schistosome

Answer 3

If the -saveState only need to execute once when active, then you can removeObserver inside the -saveState.

Gilles

Presumably, he would want to save again if the app becomes active and then resigns active again. – Linger

You are right. I assuem he will register as an observer again when the app become active. – Gilles

I just used saveState as an example, but it would probably need to be called over and over again (for example when the app will enter the background) so I like using dealloc better. – Schistosome