NSNotificationCenter and safe multithreading

Question

Given that objects may be deallocated even while a method invocation is in progress (link)*, is it safe for an object to register for and receive notificati

Answer 1

NSNotificationCenter does not take a strong reference to the object, so the observer must be removed before deallocation. When ARC is enabled, if handleNotification is being called, the observer will not be deallocated since calling handleNotification will increase its retain count. If observer is deallocated before the notification is posted, NSNotificationCenter will remove it from the observers as you write in dealloc method so that handleNotification will not be called. NSNotificationCenter calls notification handlers synchronously while notification is posted.