CODEWITHSUNDEEP
cocoa
user396030
user396030

Reputation: 263

NSNotificationCenter: Why bother calling removeObserver?

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?

Upvotes: 23

Views: 4814

Answers (2)

Steven Kramer
Steven Kramer

Reputation: 8513

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.

Upvotes: 8

Tom Dalling
Tom Dalling

Reputation: 24115

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.

Upvotes: 36

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