andrewsardone already gave you a hint but allow me to say a bit more: If you look at the Key Value Observing Protocol you will find two methods that allow you

andrewsardone already gave you a hint but allow me to say a bit more: If you look at the Key Value Observing Protocol you will find two methods that allow you to remove an observer again (remember: You have to remove an observer at the appropriate time - otherwise you will receive exceptions and your app will probably crash): removeObserver:forKeyPath: and removeObserver:forKeyPath:context:. The first one has been around forever but it does not allow you to specify a context - only an observer and a path. This is problematic and andrewsardone gave you an example. This is why Apple introduced the second method in 10.7/iOS 5 which allows you to specify a (unique) context. The documentation says: "Examining the value in context you are able to determine precisely which addObserver:forKeyPath:options:context: invocation was used to create the observation relationship. When the same observer is registered for the same key-path multiple times, but with different context pointers, an application can determine specifically which object to stop observing." Always specifying a context makes your app more robust.