Difference between Delegate and Notifications in iOS

One-to-one communicationOne-to-many or many-to-many communication
Customized behaviorBroadcasting information/events
Delegate object holds a referenceObserving objects don’t need references
Specific responsibilities/tasksWidely distributed information/events
Tight coupling between objectsLoose coupling between objects
Object needs to know its delegatePosting object doesn’t know receivers
Callbacks, data source protocols, event handlingApplication-wide event handling