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POFetchedResultsController doesn't see the changes in managedObjectContext after data import
 

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  1. POFetchedResultsController doesn't see the changes in managedObjectContext after data import
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    <p>I'm working on the data import part in my app, and to make the UI more reliable, i followed this Marcus Zarra article <a href="http://www.cimgf.com/2011/08/22/importing-and-displaying-large-data-sets-in-core-data/" rel="nofollow">http://www.cimgf.com/2011/08/22/importing-and-displaying-large-data-sets-in-core-data/</a></p> <p>The idea is that you make the import in a separate context in the background tread(i use GCD for that), and your fetchedResultsController's context merges the changes by observing the <strong>NSManagedObjectContextDidSaveNotification</strong>.</p> <p>The issue i get is very strange to me - my fetchedResultsController doesn't get those changes itsef and doesn't reload the TableView when the new data comes. But if i fire the following method, which makes the fetch and reloads the table - it gets it all there.</p> <pre><code>- (void)updateUI { NSError *error; if (![[self fetchedResultsController] performFetch:&amp;error]) { NSLog(@"Unresolved error %@, %@", error, [error userInfo]); } [self.tableView reloadData]; } </code></pre> <p>So now i call that method when i get the <strong>NSManagedObjectContextDidSaveNotification</strong> to make it work, but it looks strange and nasty to me.</p> <pre><code> - (void)contextChanged:(NSNotification*)notification { if ([notification object] == [self managedObjectContext]) return; if (![NSThread isMainThread]) { [self performSelectorOnMainThread:@selector(contextChanged:) withObject:notification waitUntilDone:NO]; return; } [[self managedObjectContext] mergeChangesFromContextDidSaveNotification:notification]; //TODO:Make it work as it should - merge, without updateUI [self updateUI];//!!!Want to get rid of this! } </code></pre> <p>Why can it be like this? Here is the code that is responsible for parsing the data and adding the Observer.</p> <pre><code>- (void)parseWordsFromServer:(NSNotification *)notification { dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0) , ^{ NSDictionary *listInJSON = [notification userInfo]; wordsNumbers = [[listInJSON valueForKey:@"words"]mutableCopy]; if ([wordsNumbers count]) { [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(contextChanged:) name:NSManagedObjectContextDidSaveNotification object:nil]; </code></pre> <p>//New Context for the new thread NSManagedObjectContext *backContext = [[AppDelegate sharedAppDelegate]backManagedObjectContext];</p> <pre><code> //Get all the words we already have on this device NSArray *wordsWeHave = [Word wordsWithNumbers:wordsNumbers inManagedContext:backContext]; //Add them to this list for (Word *word in wordsWeHave) [[List listWithID:[currentList listID] inManagedObjectContext:backContext]addWordsObject:word]; [backContext save:nil];!//Save the context - get the notification } }); } </code></pre> <p><strong>EDIT</strong> I use the <code>NSFetchedResutsControllerDelegate</code>, indeed, how else could i pretend my tableview to be updated if i didn't?</p> <p><strong>UPDATE</strong> Decided just to move to Parent - Child paradigm</p>
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    1. USNikita Pestrov
    1. USNikita Pestrov
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