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POSubclassed UITableViewCell Creates Zombie Unless Retained
 

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    <p>I've created a UITAbleViewCell subclass with a custom nib, and am using it in two different UITableViews in my app. It works perfectly in one of the tables, but the other table crashes when I scroll it vigorously. Instruments identifies a zombie in this code (in cellForRowAtIndexPath):</p> <pre><code>NSString *identifier = @"edit"; LogTableCell *cell = (LogTableCell*)[tableView dequeueReusableCellWithIdentifier:identifier]; if (!cell) { cell = (LogTableCell*) [[[NSBundle mainBundle] loadNibNamed:@"LogTableCell" owner:self options:nil] objectAtIndex:0]; [cell retain]; // prevents zombies! } NSLog(@"%@: retainCount: %d", identifier, [cell retainCount]); // some other cell init stuff return cell; </code></pre> <p>Notice the [cell retain]; line - when it's in there, the code works swimmingly. Take it out, and crash. NSLog always reports a retainCount of 2, so it shouldn't be necessary. But if I do something like this:</p> <pre><code> if ([cell retainCount] &lt; 1) { [cell retain]; } // does not prevent zombies! </code></pre> <p>it doesn't work. There's no alloc/init, so I shouldn't have to do an autorelease or worry about this at all, and I've always thought that cellForRowAtIndexPath releases the cell for me.</p> <p>When I'm not using Instruments, here's the error I get from xcode:</p> <pre><code>*** -[CALayer retain]: message sent to deallocated instance 0x4d8e930 </code></pre> <p>Even though it works with the [cell retain]; line, it looks like a leak to Analyze (and to me), so I'd like to resolve the problem. Anyone know what's going on here?</p>
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    1. COI figured it out with a little sleuthing. The problem was happening in the sublcassed UITableViewCell's dealloc. I had a handful of instance variables, and a handful of properties, all of which I was releasing in dealloc. But some of the properties were @synthesized to some of those instance variables, and when they're paired up that way, they collectively only need to be released once. So I commented out the instance variable releases that were tied to properties, and it fixed the problem. I hope this helps somebody!
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    2. COIt's a good idea to avoid using properties in your dealloc method. A property call can have unwanted side-effects. Releasing your ivar avoids any potential issues.
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    3. COIt isn't a huge issue, lots of people release variables via properties and Apple even does it in some of their example code... but all things being equal, directly access the iVar.
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