Multiple delegates for one object? (follow-up)

Question

On the question Multiple delegates per one object? one of the answers came up with interesting solution (at least for my naive eyes) : creating a "delegate splitter" that allows an object (in this case UIScrollView) to have multiple delegates (in this case UIScrollViewDelegate).

The code is as follows:

@interface DelegateSplitter : NSObject

-(void)addDelegate:(id)delegate;
-(void)addDelegates:(NSArray*)array;

@end


@interface DelegateSplitter()

@property NSMutableSet *delegates;

@end

@implementation DelegateSplitter

-(id)init
{
   self = [super init];
   _delegates = [NSMutableSet set];
   return self;
}

-(void)addDelegate:(id)delegate
{
  [_delegates addObject:delegate];
}

-(void)addDelegates:(NSArray *)array
{
   [_delegates addObjectsFromArray:array];
}

-(void)forwardInvocation:(NSInvocation *)anInvocation
{
  for (id delegate in _delegates)
  {
     if([delegate respondsToSelector:anInvocation.selector])
     {
        [anInvocation invokeWithTarget:delegate];
     }
   }
}

- (NSMethodSignature*) methodSignatureForSelector: (SEL) selector
{
  NSMethodSignature *our = [super methodSignatureForSelector:selector];
  NSMethodSignature *delegated = [[_delegates anyObject]
                                  methodSignatureForSelector:selector];
  return our ? our : delegated;
}

- (BOOL) respondsToSelector: (SEL) selector
{
   return [[_delegates anyObject] respondsToSelector:selector];
}

The problem with this code is that it creates retain cycles, and unlike a normal delegate, you can't declare it as

@property (assign) DelegateSplitter *splitter;

It does seem however a "better" solution than a wrapper. So is there anyway to avoid the retain cycle ?

score 1 · Accepted Answer · answered May 14 '13 at 13:21

how many delegates are you going to ever need, just make a property for 3 of them and if you have need for more then you need to radically redesign your app...

a much better approach is to have a delegate for each activity, a view delegate, a data source, and some asynchronous network delegate, etc... if they end up being the same object, who cares... it will just work.

Multiple delegates for one object? (follow-up)

1 Answers1