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    <p>The way I've solved this problem in the past is to use a subclass of NSProxy to break the cycle. I'll have an object that stores a weak reference to one of the arrays and passes all messages except memory management ones through to it.</p> <pre><code> ┌──── NSArray A &lt;────┐ │ │ │ │ v weak │ ACWeakProxy ┈ ┈ ┈ ┈ ┈ &gt; NSArray B </code></pre> <hr> <pre><code>@interface ACWeakProxy : NSProxy { id _object; } @property(assign) id object; - (id)initWithObject:(id)object; @end </code></pre> <hr> <pre><code>@implementation ACWeakProxy @synthesize object = _object; - (id)initWithObject:(id)object { // no init method in superclass _object = object; return self; } - (BOOL)isKindOfClass:(Class)aClass { return [super isKindOfClass:aClass] || [_object isKindOfClass:aClass]; } - (void)forwardInvocation:(NSInvocation *)invocation { [invocation setTarget:_object]; [invocation invoke]; } - (NSMethodSignature *)methodSignatureForSelector:(SEL)sel { return [_object methodSignatureForSelector:sel]; } @end </code></pre> <hr> <p>Then your code becomes</p> <pre><code>NSMutableArray * A = [[NSMutableArray alloc] initwithObjects:@"one", nil]; NSMutableArray * B = [[NSMutableArray alloc] initwithObjects:@"two", nil]; [A addObject:B]; ACWeakProxy * proxy = [[ACWeakProxy alloc] initWithObject:A]; [B addObject:proxy]; [proxy release]; // will print "two" NSLog(@"%@", [[[B objectAtIndex:1] objectAtIndex:1] objectAtIndex:0]); </code></pre> <p>It is, however, up to you to make sure your weak reference doesn't vanish while you are still using it.</p>
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    1. POHow to create weak reference in Objective-C?
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    1. COThis solution works well with ARC's weak references. If you declare your property (and ivar) as weak the value becomes nil when the reference is lost. `@property(weak) id object;`
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      1. USDavid V
    2. COWow I didn't know about NSProxy...thank you for this.
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      1. USzakdances
 

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