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POObjective-C with ARC: Custom setter does not retain
 

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    <blockquote> <p><strong>NOTE: This was due to a bug in some XCode beta versions that has long been fixed. This Question and answer will probably not help you if you have problems with ARC.</strong></p> </blockquote> <hr> <p>I am migrating my project from manual reference counting to ARC, and have stumbled upon a problem: <strong>How can I ensure that a custom setter for a retain property actually retains?</strong></p> <p>In <code>myClass.h</code>, I've declared a property: <code>@property (retain) NSDate *date</code>. It doesn't matter whether I manually set a <code>__strong</code> ivar or have it autogenerated.</p> <p>In the implementation, I have of course <code>@synthesize date</code>, and implemented a custom setter (or just <a href="https://github.com/fzwo/ARC-SetterTest" rel="nofollow">download the demo Xcode project</a>):</p> <pre><code>- (void)setDate:(NSDate *)newDate { if (allowedToSetNewDate) { date = newDate; } } </code></pre> <p>This does not seem to retain the date, and gives me <code>message sent to deallocated instance</code> when newName is (auto-) released where it came from, when trying to access <code>myClass.date</code> later (provided Zombie is enabled; otherwise, it just crashes silently).</p> <p>Changing the setter to use <code>date = [newDate copy]</code> works around the error, but isn't really what I want. Deleting the custom setter also works, but is obviously not desireable.</p> <p>What am I missing here? How can I ensure that a custom setter for a retain property actually retains in an ARC environment? This seems such a basic and common task that I think I'm overlooking something very obvious.</p> <p>(NOTE: This does not fall under the terms of any Apple NDA, as ARC is publically released as part of LLVM)</p> <p>EDIT: I've created a small Xcode project to demo the issue and uploaded it to github. Feel free to <a href="https://github.com/fzwo/ARC-SetterTest" rel="nofollow">download it</a> and play around. I'm at my wit's end (though my wit is not at its best today, admittedly).</p> <p>EDIT: For this sample project, this problem is solved (see accepted answer). Unfortunately, in the bigger project, which I am not at liberty to share, the problem persists. As a workaround, I've added duplicate <code>strong</code> properties with synthesized setters (ivars don't work). The new custom setter now looks like this:</p> <pre><code>- (void)setDate:(NSDate *)newDate { if (allowedToSetNewDate) { self.date_arcretain = newDate; //this property is only there as a workaround. ARC properly retains it, but only if the setter is synthesized date = newDate; } } </code></pre>
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    1. COThis may help a little, pertaining the use of (nonatomic, retain) that you should perhaps be calling on your NSString: http://stackoverflow.com/questions/1380338/objective-c-101-retain-vs-assign-nsstring
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    2. CO@Luke, I don't see what that has to do with this question. I do understand how retain counting works, and what property declarations mean - as I have written in the question, I am migrating from a project (with manual counting, not GC - will add this) to ARC. EDIT: I see now, you mean that strings should be `copy`d. I'll update my example, because this does not only concern strings.
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    3. CONot quite sure, but I think you have to qualify the `newDate` parameter as `__strong`.
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