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    <p>Well this is a strange one but I have got it doing what I need now. When I start the background task updating I pass it its own NSManagedObjectContext. I set my main thread as a subscriber to the save event in this NSManagedObjectContext so that I can update the main threads MOC when the background MOC actions a save.</p> <pre><code>- (void)mergeChanges:(NSNotification *)notification { DLog(@"Merge changes has begun"); // Merge changes into the main context on the main thread NSManagedObjectContext *incommingContext = [notification object]; if (incommingContext != self.managedObjectContext){ dispatch_sync(dispatch_get_main_queue(), ^{ [self.managedObjectContext mergeChangesFromContextDidSaveNotification:notification]; }); } //[self compareMOCs]; } </code></pre> <p>When you action <code>NSManagedObjectContext rollback</code> the NSManagedObjectContext does not roll back (because it is saved) but the NSFetchedResultsController does and shows up the two deleted records. </p> <p>To work around this I am having to save my main threads NSManagedObjectContext in the main thread after a save merge as so:</p> <pre><code>- (void)mergeChanges:(NSNotification *)notification { DLog(@"Merge changes has begun"); // Merge changes into the main context on the main thread NSManagedObjectContext *incommingContext = [notification object]; if (incommingContext != self.managedObjectContext){ dispatch_sync(dispatch_get_main_queue(), ^{ [self.managedObjectContext mergeChangesFromContextDidSaveNotification:notification]; // no idea why I have to do this but if I do not do this any // attempt to rollback the MOC will cause the NSFetchedResultsController to pull out // ghost records. [self.managedObjectContext save:nil]; }); } //[self compareMOCs]; } </code></pre> <p>According to Apple this should not be required as the notification is only fired after a save event on the background MOC. I cannot explain why this is happening, I can only tell you that it is happening and this extra save has fixed it.</p>
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    1. USCraig Moore
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