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PODoes CoreData allow object graph loops? (Strange error)
 

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  1. PODoes CoreData allow object graph loops? (Strange error)
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    <p>I've been having a strange problem with CoreData for a while now. This will be a lenghty question, so bear with me... </p> <p>I have two Entites, call them A and B. B might be both creator and updater of several A's. A must have a B as creator, and may or may not have a B as updater. (Required and optional relationships.) </p> <p>B might have both created and updated zero or more A's. </p> <p><img src="https://i.stack.imgur.com/HT14k.png" alt="With inverse relationships"></p> <p>The above is the data model I built. (I don't really <em>need</em> the inverse relationship from B to A, but CoreData gives me compile time warnings otherwise.) </p> <p><strong>EDIT</strong></p> <p>Here are the relevant parts of the ManagedObject subclasses: </p> <p>A.h</p> <pre><code>@property (nonatomic, retain) B * creator; @property (nonatomic, retain) B * updater; </code></pre> <p>A.m</p> <pre><code>@dynamic creator; @dynamic updater; </code></pre> <p>B.h</p> <pre><code>@property (nonatomic, retain) NSSet * created; @property (nonatomic, retain) NSSet * updated; </code></pre> <p>B.m</p> <pre><code>@dynamic updated; @dynamic created; - (void)addUpdatedObject:(A *)value { NSSet *changedObjects = [[NSSet alloc] initWithObjects:&amp;value count:1]; [self willChangeValueForKey:@"updated" withSetMutation:NSKeyValueUnionSetMutation usingObjects:changedObjects]; [[self primitiveValueForKey:@"updated"] addObject:value]; [self didChangeValueForKey:@"updated" withSetMutation:NSKeyValueUnionSetMutation usingObjects:changedObjects]; [changedObjects release]; } - (void)removeUpdatedObject:(A *)value { NSSet *changedObjects = [[NSSet alloc] initWithObjects:&amp;value count:1]; [self willChangeValueForKey:@"updated" withSetMutation:NSKeyValueMinusSetMutation usingObjects:changedObjects]; [[self primitiveValueForKey:@"updated"] removeObject:value]; [self didChangeValueForKey:@"updated" withSetMutation:NSKeyValueMinusSetMutation usingObjects:changedObjects]; [changedObjects release]; } - (void)addUpdated:(NSSet *)value { [self willChangeValueForKey:@"updated" withSetMutation:NSKeyValueUnionSetMutation usingObjects:value]; [[self primitiveValueForKey:@"updated"] unionSet:value]; [self didChangeValueForKey:@"updated" withSetMutation:NSKeyValueUnionSetMutation usingObjects:value]; } - (void)removeUpdated:(NSSet *)value { [self willChangeValueForKey:@"updated" withSetMutation:NSKeyValueMinusSetMutation usingObjects:value]; [[self primitiveValueForKey:@"updated"] minusSet:value]; [self didChangeValueForKey:@"updated" withSetMutation:NSKeyValueMinusSetMutation usingObjects:value]; } - (void)addCreatedObject:(A *)value { NSSet *changedObjects = [[NSSet alloc] initWithObjects:&amp;value count:1]; [self willChangeValueForKey:@"created" withSetMutation:NSKeyValueUnionSetMutation usingObjects:changedObjects]; [[self primitiveValueForKey:@"created"] addObject:value]; [self didChangeValueForKey:@"created" withSetMutation:NSKeyValueUnionSetMutation usingObjects:changedObjects]; [changedObjects release]; } - (void)removeCreatedObject:(A *)value { NSSet *changedObjects = [[NSSet alloc] initWithObjects:&amp;value count:1]; [self willChangeValueForKey:@"created" withSetMutation:NSKeyValueMinusSetMutation usingObjects:changedObjects]; [[self primitiveValueForKey:@"created"] removeObject:value]; [self didChangeValueForKey:@"created" withSetMutation:NSKeyValueMinusSetMutation usingObjects:changedObjects]; [changedObjects release]; } - (void)addCreated:(NSSet *)value { [self willChangeValueForKey:@"created" withSetMutation:NSKeyValueUnionSetMutation usingObjects:value]; [[self primitiveValueForKey:@"created"] unionSet:value]; [self didChangeValueForKey:@"created" withSetMutation:NSKeyValueUnionSetMutation usingObjects:value]; } - (void)removeCreated:(NSSet *)value { [self willChangeValueForKey:@"created" withSetMutation:NSKeyValueMinusSetMutation usingObjects:value]; [[self primitiveValueForKey:@"created"] minusSet:value]; [self didChangeValueForKey:@"created" withSetMutation:NSKeyValueMinusSetMutation usingObjects:value]; } </code></pre> <p><strong>END EDIT</strong></p> <p>When I create a new A with a B as creator, everything is fine (when using inverse relationships). However, when I update that same A later, using the same B as creator, i get the following crash: </p> <pre><code>2011-05-05 13:17:40.885 myapp[27033:207] -[NSCFNumber count]: unrecognized selector sent to instance 0x5d14eb0 2011-05-05 13:17:40.887 myapp[27033:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSCFNumber count]: unrecognized selector sent to instance 0x5d14eb0' *** Call stack at first throw: ( 0 CoreFoundation 0x014065a9 __exceptionPreprocess + 185 1 libobjc.A.dylib 0x0155a313 objc_exception_throw + 44 2 CoreFoundation 0x014080bb -[NSObject(NSObject) doesNotRecognizeSelector:] + 187 3 CoreFoundation 0x01377966 ___forwarding___ + 966 4 CoreFoundation 0x01377522 _CF_forwarding_prep_0 + 50 5 CoreFoundation 0x013b7c3b -[NSSet intersectsSet:] + 59 6 Foundation 0x00c3f4fb NSKeyValueWillChangeBySetMutation + 422 7 Foundation 0x00c0416d NSKeyValueWillChange + 400 8 Foundation 0x00c3f34d -[NSObject(NSKeyValueObserverNotification) willChangeValueForKey:withSetMutation:usingObjects:] + 315 9 CoreData 0x01172bd0 -[NSManagedObject willChangeValueForKey:withSetMutation:usingObjects:] + 112 10 myapp 0x0004fd48 -[B addUpdatedObject:] + 168 11 CoreData 0x011729f2 -[NSManagedObject(_NSInternalMethods) _includeObject:intoPropertyWithKey:andIndex:] + 98 12 CoreData 0x01169301 -[NSManagedObject(_NSInternalMethods) _didChangeValue:forRelationship:named:withInverse:] + 497 13 Foundation 0x00c051e4 NSKeyValueNotifyObserver + 361 14 Foundation 0x00c04ca6 NSKeyValueDidChange + 384 15 Foundation 0x00beb3e2 -[NSObject(NSKeyValueObserverNotification) didChangeValueForKey:] + 123 16 CoreData 0x01166adb _PF_ManagedObject_DidChangeValueForKeyIndex + 171 17 CoreData 0x01165de9 _sharedIMPL_setvfk_core + 313 18 CoreData 0x01173997 _svfk_11 + 39 </code></pre> <p>(Yes, <em>B</em> has the method <code>addUpdatedObject</code>defined.) </p> <p>For further background, the list of A:s are shown in a <code>UITableView</code> backed by a <code>NSFetchedResultsController</code>. </p> <p>The strangest thing is, IMHO, that it's perfectly possible to add a new A (with B as creator) with the inverse relationship without it leading to a crash, while adding the same B as updater to that same A leads to a crash. </p> <p>However, when I remove the inverse relationships, everything works as expected. </p> <p><img src="https://i.stack.imgur.com/rmHBe.png" alt="Without inverse relationships"></p> <p>I can add the same B as A:s creator and updater without any problems, and the app works as it should, except for the build-time warnings from CoreData:</p> <pre><code>A.creator should have an inverse A.updater should have an inverse </code></pre> <p>So, is there any CoreData guru out there that can explain why the first case breaks? </p>
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