How do I create delegates in Objective-C?

Question

I know how delegates work, and I know how I can use them.

But how do I create them?

Answer 1

As a good practice recommended by Apple, it's good for the delegate (which is a protocol, by definition), to conform to NSObject protocol.

@protocol MyDelegate 
    ...
@end

& to create optional methods within your delegate (i.e. methods which need not necessarily be implemented), you can use the @optional annotation like this :

@protocol MyDelegate 
    ...
    ...
      // Declaration for Methods that 'must' be implemented'
    ...
    ...
    @optional
    ...
      // Declaration for Methods that 'need not necessarily' be implemented by the class conforming to your delegate
    ...
@end

So when using methods that you have specified as optional, you need to (in your class) check with respondsToSelector if the view (that is conforming to your delegate) has actually implemented your optional method(s) or not.