Non-retaining array for delegates

Question

In a Cocoa Touch project, I need a specific class to have not only a single delegate object, but many of them.

It looks like I should create an NSArray for these del

Answer 1

I found this bit of code awhile ago (can't remember who to attribute it to).

It's quite ingenius, using a Category to allow the creation of a mutable array that does no retain/release by backing it with a CFArray with proper callbacks.

@implementation NSMutableArray (WeakReferences)
    + (id)mutableArrayUsingWeakReferences {
    return [self mutableArrayUsingWeakReferencesWithCapacity:0];
    }

    + (id)mutableArrayUsingWeakReferencesWithCapacity:(NSUInteger)capacity {
    CFArrayCallBacks callbacks = {0, NULL, NULL, CFCopyDescription, CFEqual};
    // We create a weak reference array
    return (id)(CFArrayCreateMutable(0, capacity, &callbacks));
    }
@end

EDIT Found the original article: http://ofcodeandmen.poltras.com

Answer 2

This one from NIMBUS would be more simple:

NSMutableArray* NICreateNonRetainingMutableArray(void) {
  return (NSMutableArray *)CFArrayCreateMutable(nil, 0, nil);
}

NSMutableDictionary* NICreateNonRetainingMutableDictionary(void) {
  return (NSMutableDictionary *)CFDictionaryCreateMutable(nil, 0, nil, nil);
}

NSMutableSet* NICreateNonRetainingMutableSet(void) {
  return (NSMutableSet *)CFSetCreateMutable(nil, 0, nil);
}

Answer 3

Check documentation of NSValue valueWithNonretainedObject method :

This method is useful for preventing an object from being retained when it’s added to a collection object (such as an instance of NSArray or NSDictionary).

Answer 4

You do not want to do this! Cocoa Touch have several concepts for sending events, you should use the proper concept for each case.

1. Target-action: For UI controls, such as button presses. One sender, zero or more receivers.
2. Delegates: For one sender and one receiver only.
3. Notification: For one sender, and zero or more receivers.
4. KVO: More fine grained that notifications.

What you should do is to look into how to use NSNotificationCenter class. This is the proper way to send a notification that have more than one receiver.