What is the purpose of an iOS delegate?

Question

I understand what a delegate does in iOS, and I\'ve looked at sample code, but I\'m just wondering about the advantages of this type of encapsulation (as opposed to includin

Answer 1

The most common use of a delegate in iOS is to establish communication within modules that are unrelated or partially related to each other. For example, passing data forward in a UINavigationController is very easy, we can just use segue. However, sending data backwards is little tricky. In this case, we can use delegate to send the data backward.

Let's call, the class, associated with the first Controller ClassA and the class, associated with the second Controller ClassB. The first Controller is connected to the second controller with a forward segue. We can pass data from ClassA to ClassB through this segue. Now, we need to pass some data to ClassA from ClassB for which we can use delegates.

The sender class(ClassB) needs to have a protocol in its header file(.h) and also a reference of it as delegate inside the block, @interface ClassB .... @end. This reference let's the ClassB know that it has a delegate. Any class that wants to use this ClassB will have to implement all of this protocol's required methods(if any). So, the receiver class,ClassA will implement the method but the call will be made by the sender class, ClassB.

This way, receiver class doesn't need to worry about the sender class' internal structure, and can receive the required information.