Question

I have a class and this class has a delegate protocol. I create an object in the main class using this class and assigned the main class as the delegate. The main class has a property I would like to read inside the created class. Then I do this:

BOOL prop = [self.delegate myProperty];

Xcode complains that “delegate may not respond to myProperty“

If I am sending a message to self.delegate to read myProperty, and generally Xcode never complains when you send a message to an not casted object, why do I have to do that

BOOL prop = [(myMainClass *)self.delegate myProperty];

to make it work?

To be more clear, here is an example of a message sent to an object without having to cast:

[self.myArray enumerateObjectsUsingBlock:^(id obj, NSUInteger index, BOOL *stop){

    int Number = [[obj dictionaryOfNames] count];

}];

self.myArray is an array of objects from another class that are dictionaries and have this property dictionaryOfNames. Xcode never asked me to cast this:

int Number = [[(myOtherClass *)obj dictionaryOfNames] count];

as I had to above for myProperty.

Answer 1

Different classes can conform to a protocol. If you declare that you conform to a protocol you just say that you will implement the requiered methods but you can implement it in a UIView, UIViewController, MyOwnClass, MyOtherClass etc.

Thats why a property is normally declared like this

@property (nonatomic, weak) id <MyProtocol> delegate;

So you just say your delegate is an object which conform to the protocol.