NSNotificationCenter addObserver not responding

Question

In my app (game) I'm trying to use the NSNotificationCenter to pause and resume the game when either the center/home or lock button is pressed. This is the code I'm using:

[[NSNotificationCenter defaultCenter]
 addObserver:self
 selector:@selector(pauseLayer:)
 name:UIApplicationWillResignActiveNotification
 object:self.view.layer.sublayers];

[[NSNotificationCenter defaultCenter]
 addObserver:self
 selector:@selector(pauseLayer:)
 name:UIApplicationDidEnterBackgroundNotification
 object:self.view.layer.sublayers];

[[NSNotificationCenter defaultCenter]
 addObserver:self
 selector:@selector(resumeLayer:)
 name:UIApplicationWillEnterForegroundNotification
 object:self.view.layer.sublayers];

I have experimented with putting it in lots of different places like viewDidLoad, viewDidAppear, initWithNibNameOrNil, but although they are all being called, the methods pauseLayer and resumeLayer never get called, even though the app delegate method does. Why doesn't this code work?

Answer 1

change the addObserver calls and remove self.view.layer.sublayers from the object param. change it to nil.

EDIT: more info

Sure. The object param tells NSNotificationCenter which object's notification you want to observe. When you specify self.view.layer.sublayers you are observing UIApplicationWillEnterForegroundNotification et al only sent by the sublayers array. Of course, the sublayers array does not send this notification. When you specify object:nil you are observing the notification from any object. That is appropriate in this case. If you want to specify an object it would be [UIApplication sharedApplication].