Previously, the method addObserverForName:object::usingBlock: didn't exist in Cappuccino.
Now it does.
To observe, you need to use the method - (id <CPObject>)addObserverForName:(CPString)aNotificationName object:(id)anObject usingBlock:(Function)block
To unregister observations, you pass the object returned by this method to removeObserver:. You must invoke removeObserver: or removeObserver:name:object:.
Test /Tests/Foundation/CPNotificationCenterTest.j
Fixed#2259
If one observer of a notification centre notification removed another observer, that other observer would still be notified even that it was no longer observing.
Now the code agrees with its comments.