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copied!<p>As already mentioned in other answers, you should pass an <code>autorelease</code>d instance to the setter like this:</p> <pre><code>[self setMediaSources: [[[MediaSources alloc] init] autorelease]]; </code></pre> <p>The crash you're seeing as a result of doing this seems to stem from the fact that you are doing background processing in <code>checkForMediaSourceUpdates</code>. If you want to do background processing in this method, you should ensure that <code>self</code> remains valid for the entire duration of the background task. It is perfectly valid to manually call <code>[self retain];</code> at the start and <code>[self release];</code> at the end. (Note: <code>GCD</code> blocks automatically retain/release <code>self</code> object if you're referencing it from within the block).</p> <p>EDIT: I hope you know the problem now, <a href="https://stackoverflow.com/users/773625/mau">mAu</a> called it. There is only one retain count (by <code>RootViewController</code> object) on <code>MediaSources</code> instance when a request is being executed. Before the request finishes, you call the method again, resulting in the <code>MediaSources</code> object being released. So when the request finishes, and <code>NSNotification</code> tries to send the callback message, app crashes since the observer instance has disappeared. </p> <p>There are two ways to resolve this (use whichever is more appropriate for your case): </p> <ol> <li>Either add <code>[self retain];</code> in <code>checkForMediaSourceUpdates</code> and <code>[self release];</code> at the end of <code>checkForMediaSourceUpdatesDownloadFinished:</code> </li> <li>Or, add <code>[[NSNotificationCenter defaultCenter] removeObserver: self]</code> in <code>-[MediaSources dealloc]</code>. </li> </ol> <p>Btw, you should think about <a href="https://stackoverflow.com/a/16677223/440060"><code>why do you need to allocate a new MediaSource on every call to getSelectedMediaSources?</code></a> and why you're starting a new request every time when you potentially have a running request. There is something very wrong with your design. </p>

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