Question

Im working on an ios app, ios 5+ , using xcode and objective c. Ok currently messing with nsnotifications and i just need some clarifications as im a wee bit confused.
Lets say i have a view controller that i add an observer to like so

 [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(showContent:) name:kTPSShowContentNotification object:self];

where the object is set to self. I took this to mean that it is only looking from that notification if sent from that object. am i wrong on that?

elsewhere in code I am positing a notification like so

 [[NSNotificationCenter defaultCenter] postNotificationName:kTPSShowContentNotification object:currentVC];

where currentVC is the view controller that has the observer set up initially.
I thought this is all that was needed to catch that notification as the post is telling the notification center to send it from that view controller. but it fails to catch it and im unsure as to why. If when adding the observer i set the object as nil then it catches it but so does all the other viewcontrollers (if any ) that have observers for that notification too. Is there any way around this ? am i approaching this completely wrong?

Answer 1

If I’m getting this right, you want to post and get a notification from the same controller. So you can do something like this:

 [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(showContent:) name:kTPSShowContentNotification object:self];

 [[NSNotificationCenter defaultCenter] postNotificationName:kTPSShowContentNotification object:self];

But it should work indeed if your currentVC ivar is pointing to the very same controller. The fact that you say it doesn’t work makes me believe that it is not pointing to the same instance of your controller.