Question

NSCollectionView has a delegate which should conform to NSCollectionViewDelegate.

- (id < NSCollectionViewDelegate >)delegate

I have a new protocol, which extends NSCollectionViewDelegate.

@protocol extendedProtocol <NSCollectionViewDelegate>

Now, in my CollectionViewItem’s controller class, I try to call the delegate’s method in this way:

if (
    [self collectionView] 
    && [[self collectionView] delegate] && 
    [[[self collectionView] delegate] conformsToProtocol:@protocol(extendedProtocol)]
        ) 
{
BOOL flag = [[[self collectionView] delegate] doSomeWork:@"abc"];
}

I keep getting warning that “Instance Method ‘doSomeWork:’ not found”.

I tried doing

id <extendedProtocol> dg = [[self collectionView] delegate];
BOOL flag = [dg doSomeWork:@"abc"];

But then I get warning, “Incompatible pointer types initializing ‘id’ with an expression of type ‘id’.

What is the correct way of changing the protocol of NSCollectionView delegate?

Answer 1

You need a cast. Either like this:

BOOL flag = [(id <extendedProtocol>) [[self collectionView] delegate] doSomeWork:@"abc"];

Or in your second example:

id <extendedProtocol> dg = (id <extendedProtocol>) [[self collectionView] delegate];