Why the Observer in NSNotification called twice....?
cocoa, notifications, objective-c
Solution
If the observer class is registered for a notification by name, but not against a specific object, it will receive multiple messages, as it will be invoked every time the notification occurs, regardless of the originating object.
Likewise, if the observer is registered against a specific object, but not against a named notification, it will be messaged every time there is a notification concerning that object.
An alternative mechanism for being informed of changes in a distant state, is Key Value observing -http://developer.apple.com/documentation/Cocoa/Conceptual/KeyValueObserving/KeyValueObserving.html
Problem
If the class is a custom class, after posting the notification, the selector corresponding to the observer is called twice.. Is there any better solution so that the selector is called only once?