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PONSRangeException exception in NSFetchedResultsChangeUpdate event of NSFetchedResultsController
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  1. PONSRangeException exception in NSFetchedResultsChangeUpdate event of NSFetchedResultsController
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    copied!<p>I have a <code>UITableView</code> that uses an <code>NSFetchedResultsController</code> as data source.</p> <p>The core data store is updated in multiple background threads running in parallel (each thread using it's own <code>NSManagedObjectContext</code>).</p> <p>The main thread observes the <code>NSManagedObjectContextDidSaveNotification</code> notification and updates it's context with <code>mergeChangesFromContextDidSaveNotification:</code>.</p> <p>Sometimes it happens that the <code>NSFetchedResultsController</code> sends an <code>NSFetchedResultsChangeUpdate</code> event with an indexPath that does not exist anymore at that point.</p> <p>For example: The result set of the fetched results controller contains 1 section with 4 objects. The first object is deleted in one thread. The last object is updated in a different thread. Then sometimes the following happens:</p> <ul> <li>controllerWillChangeContent: is called.</li> <li>controller:didChangeObject:atIndexPath:forChangeType:newIndexPath: is called with type = NSFetchedResultsChangeDelete, indexPath.row = 0.</li> <li>controller:didChangeObject:atIndexPath:forChangeType:newIndexPath: is called with type = NSFetchedResultsChangeUpdate, indexPath.row = 3.</li> </ul> <p>But the fetched results controller contains only 3 objects now, and if call</p> <pre><code>MyManagedObject *obj = [controller objectAtIndexPath:indexPath] </code></pre> <p>to update the table view cell according to the <code>NSFetchedResultsChangeUpdate</code> event, this crashes with a <code>NSRangeException</code> exception.</p> <p>Thank you for any help or ideas!</p>
 

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