Can protocols within protocols be treated as inclusive of the protocol they adopt?

Question

I am assigning protocols in a couple classes that follow an inheritance tree. Like so:

first class

@protocol LevelOne
- (void) functionA
@end

@interface BaseClass : NSObject <LevelOne> {
}

second class

@protocol LevelTwo <LevelOne>
- (void) functionB
@end

@interface SubClass : BaseClass <LevelTwo> {
}

Later I am assigning the class as delegate properties of other classes

base class

@interface AppClass : NSObject {
    @protected
    id<LevelOne> levelOneDelegate;
}

@property (assign) id<LevelOne> levelOneDelegate;

subclass

@interface AppClassesFriend : AppClass {
    @protected
    id<LevelTwo> levelTwoDelegate;
}

@property (assign) id<LevelTwo> levelTwoDelegate;

At the end of this journey, AppClassesFriend has 2 properties on it.

"levelOneDelegate" has access to "functionA", when it is assigned with a BaseClass object.

However, I am finding that "levelTwoDelegate" only has access to "functionB" (it is assigned with a SubClass object).

In order to have AppClassesFriend be able to use both functions, it seems I need to assign BOTH a levelOneDelegate AND levelTwoDelegate.

Is there any way to make "levelTwoDelegate" have access to both? Since, both functions are available on "SubClass".

So, what I would like to be able to do is :

SubClass *s = [SubClass alloc];
AppClassesFriend *a = [AppClassesFriend alloc];
a.levelTwoDelegate = s;

so inside AppClassesFriend (a) I could use :

 [self.levelTwoDelegate functionA];   <---- this is never found
 [self.levelTwoDelegate functionB];

but it seems I have to add

a.levelOneDelegate = s;

Thanks if anyone took the time to read all the way down this far. So in summary the question is, how do I get "levelTwoDelegate" to have access to both functionA and functionB?

Answer 1

Simply declare that your subclass's delegate property implements both level one and level two protocols (i.e. implements both functionA and functionB):

@interface AppClassesFriend : AppClass {
    @protected
    id<LevelOne,LevelTwo> levelOneAndTwoDelegate;
}

@property (assign) id<LevelOne,LevelTwo> levelOneAndTwoDelegate;