NSNotificationCenter Block-based Observer
Back in iOS 4, a nifty block-based observer method was added to NSNotificationCenter: (id)addObserverForName:(NSString *)name object:(id)obj queue:(NSOperationQueue *)queue usingBlock:(void (^)(NSNotification *))block; Super convenient, right? I love using blocks to pass simple callbacks to controllers instead of creating a delegate protocol. There is a catch with this method, and it's not terribly obvious unless you're looking closely. The method returns (id) - according to Apple's documentation the return object is "An opaque object to act as the observer". What does this mean? ...