Question

I have subclassed a UIScrollView to customize it a bit. I am trying to create a delegate that will notify several other classes that a user has done a certain thing in the UIScrollView. In my UIScrollView class I have the code below. The problem I am running into is I am getting the warning

Property ‘delegate’ ‘retain (or strong)’ attribute does not match the
property inherited from ‘UIScrollView’

I see that this is because my Class in inheriting from UIScrollView, but my delegate is conforming to the NSObject. This is the first time I tried creating my own delegate. What can I do to fix this?

My Code:

#import <UIKit/UIKit.h>

@protocol ChangeSpaceDelegate <NSObject>
- (void)changeSpace:(int)spaceId;

@end

@interface CustomUIScrollView : UIScrollView {
    id<ChangeSpaceDelegate> delegate;
}

@property (retain, nonatomic)id delegate;

@end

Answer 1

To answer your question specifically, you are redefining the property attribute on the delegate property you get from UIScrollView. It should, like all delegates, be weak (or, pre-iOS 5, unsafe_unretained).

However, you shouldn’t do it this way. UIScrollView already has a delegate, and if you expect to put your own delegate object implementing your new delegate methods into it, the inner workings of UIScrollView aren’t going to be happy. Define a new protocol and a new delegate property for it.

@property (weak, nonatomic) id<ChangeSpaceDelegate> changeSpaceDelegate;