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POWhy is my Objective-C object being deallocated?
 

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  1. POWhy is my Objective-C object being deallocated?
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    <p>I have a problem with an Objective-C object (in an iOS game app) that is being mysteriously deallocated.</p> <p>The object is a GameCharacter instance which is instantiated like so:</p> <pre><code>for (int c = 0; c &lt; kNrOfGuards; c++) { GameCharacter* guard = [[GameCharacter alloc] initGuard:self sprite:guardSprite]; [characterArray addObject:guard]; [guard release]; } </code></pre> <p>I also have a convenience method for finding a GameCharacter:</p> <pre><code>- (GameCharacter*)findCharacterWithIndex:(int)index { return [characterArray objectAtIndex:index]; } </code></pre> <p>And the code that generates the error looks like:</p> <pre><code>for (int c = 0; c &lt; [self characterCount]; c++) { GameCharacter* tempCharacter = [self findCharacterWithIndex:c]; if (tempCharacter.playerId == playerIndex]) { ... } } </code></pre> <p>Running this code <em>for some time</em> (never immediately) generates an error in the Console:</p> <p><strong>[GameCharacter playerId]: message sent to deallocated instance 0x4e47560</strong></p> <p>With the <a href="http://www.codza.com/how-to-debug-exc_bad_access-on-iphone" rel="nofollow">NSZombieEnabled trick</a> I've managed to track down the object(s) that is causing the problem, but I still can't understand <em>why</em> this object is being deallocated. Searching my code for "release"/"dealloc" does not produce any clues.</p> <p>I've tried removing the "release" (and even adding a "retain"!) to the alloc/init loop (see top), it seems to extend the time the app can run but not remove the problem entirely.</p> <p>Any hints would be much appreciated!</p> <p><strong>EDIT</strong></p> <p>Thanks to quixoto, Olie, Eiko, tc., I've figured out that it is my GameCharacter object that is being deallocated, but I still don't understand quite why. Here is the trace log in reverse chronological order:</p> <pre><code>#0 -[GameCharacter dealloc] #1 objc_setProperty #2 -[TiledGroundLayer setSelectedCharacter:] #3 -[TiledGroundLayer selectNextCharacterForPlayer:searchStep:] #4 -[GameScene selectNextCharacter:] #5 -[GameScene endTurn] #6 -[HUDLayer onClickDone:] </code></pre> <p>What happens here, is that the user clicks "Done", the selected character on screen is changed and thus the property <code>selectedCharacter</code> on TiledGroundLayer (step #2-4). Since <code>selectedCharacter</code> owns the previous GameCharacter object, it seems it is being deallocated. But why is it not being retained properly by the NSMutableArray (<code>[characterArray addObject:guard];</code>)?</p>
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    1. USTom Söderlund
    1. USTom Söderlund
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    1. COWas your characterArray variable created as `[NSMutableArray array]` or `[[NSMutableArray init] alloc]`?
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      1. POWhy is my Objective-C object being deallocated?
      1. UStidwall
    2. CO@Tom - in which classes do these code snippets live? It looks like you have code elsewhere that interacts with the characterArray resulting in the dealloc. Could be associated with removal of the object from the array for example - does that happen?
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      1. USmartin clayton
    3. COI would look carefully at characterArray and when it is deallocated. Since you have a convenience function to return a guard you could easily be holding onto it after characterArray and all its contents are deallocated. If you didn't have the convenience method (and I can't see its benefit here) you could instead just grab the guard from the array whenever you need it and be more sure that characterArray was still required and valid at that point.
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      1. USAdam Eberbach
 

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