Difference between Delegate and NSNotification

Ans :  A delegate uses protocol and creates a has-a relationship between two classes. Benefit of delegate is that we can return something back to the owning class.

Notification is like point to multi-point communication. Notification is one way  of message transmitting way.

Delegates create relationship between two classes. Notifications are used to send events to one or many classes.

We have to use delegate to specified known object. Notification for all object.

Delegate is like talking over telephone. Notification is like radio station.  

Coding of NSNotificationCenter :

[[NSNotificationCenter defaultCenter] addObjserver:self selector:@selector(useNotificationWithString:)  name:@”TimeOut” object:nil];

For BroadCast,

[[NSNotificationCenter defaultCenter] postNotificationName:@”TimeOut” object:nil userInfo:dict];

-(void) useNotificationWithString:(NSNotification *)notification

{

            dict = [notification userInfo];

}

To Remove observer,

[[NSNotificationCenter defaultCenter] removeObserver];

Coding of Delegate