Delegate  and notification is a  means of communication between objects of iOS applications. A delegate is for one-to-one (bidirectional) communication. In delegation the class raising events will have a property for the delegate and will typically expect it to implement some protocol.The broadcasting class  does not need to know anything about the listeners for this event, so notification is  useful in helping to decouple components in an application. Notification allows a class to broadcast events across the entire application. Notifications are for to-many, unidirectional communication.