Intercept Objective-C delegate messages within a subclass

Question

I have a subclass of UIScrollView in which I need to internally respond to scrolling behaviour. However, the viewcontroller will still need to listen to scrolling delegate c

Answer 1

Actually, this worked for me:

@implementation MySubclass {
    id _actualDelegate;
}

// There is no need to set the value of _actualDelegate in an init* method
- (void)setDelegate:(id)newDelegate {
    [super setDelegate:nil];
    _actualDelegate = newDelegate;
    [super setDelegate:(id)self];
}

- (id)delegate {
    return self;
}

- (id)forwardingTargetForSelector:(SEL)aSelector {
    if ([_actualDelegate respondsToSelector:aSelector]) { return _actualDelegate; }
    return [super forwardingTargetForSelector:aSelector];
}

- (BOOL)respondsToSelector:(SEL)aSelector {
    return [super respondsToSelector:aSelector] || [_actualDelegate respondsToSelector:aSelector];
}
@end

...making the subclass to be the message interceptor in the awesome answer given by e.James.