NSNotificationCenter: Why bother calling removeObserver?

Question

The gods have parachuted many habits into my isolated jungle village, such as:

- (void) dealloc {    [[NSNotificationCenter defaultCenter] removeObserver:self];   [super dealloc];  } 

Their ways are strange to me, yet I still seek to understand them.

Why bother cleaning loose ends up if the instance is going away? Will the reference/retain count to that instance not be decremented? Will it clutter some sort of Notification Hash Table lurking out there that holds a list of all the listeners?

Answer 1

NSNotificationCenter doesn't retain observers. If you don't remove the observer, and the observer is deallocated, then NSNotificationCenter is left holding a dangling pointer which will (most often) crash when it next tries to notify the observer.

Answer 2

Although in practice many of your uninitiated younglings will get away without following the rites, because it has pleased St. Jobs to bestow a removeObserver incantation upon many of your super classes. Such as UINavigationController. Although this is not found in any the Writings I have found this to be true.