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PONSSortdescriptor ineffective on fetch result from NSManagedContext
 

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    <p>I'm trying to sort my NSFetchRequest result using a NSSortdescriptor using a key pointing to a NSDate value. My fetch results come out totally random for no clear reason.</p> <p>The NSManagedObjectContext I'm using is updated with a save from a nested child context created on a subclass of NSOperation. I know all this is done successfully because I can get all the data needed from the parent (main) context. Fetching from it just wont sort on date!</p> <p>Strange thing is; predicates for selecting the entities (called "Tweet") between two dates works just fine!</p> <p>Here's some code to illustrate my problem:</p> <pre><code>NSSortDescriptor* timeDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"time" ascending:NO selector:@selector(compare:)]; NSFetchRequest* request = [NSFetchRequest fetchRequestWithEntityName:@"Tweet"]; [request setSortDescriptors:[NSArray arrayWithObjects:timeDescriptor, nil]]; NSPredicate* predicate = [NSPredicate predicateWithFormat:@"((time &gt;= %@) AND (time &lt;= %@))",startDate,endDate]; [request setPredicate:predicate]; NSManagedObjectContext* context = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType]; [context setParentContext:[[NSApp delegate] managedObjectContext]]; [context performBlock:^{ NSError* error = nil; NSArray* results = nil; results = [context executeFetchRequest:request error:&amp;error]; // Results here are not ordered correctly // 2nd try sorting results using fetched array (works!) results = [results sortedArrayUsingDescriptors:[NSArray arrayWithObjects:timeDescriptor, nil]]; // This works too but not needed anymore /*results = [results sortedArrayUsingComparator:^(id obj1, id obj2) { Tweet* tweet1 = (Tweet*)obj1; Tweet* tweet2 = (Tweet*)obj2; //return [tweet1.time compare:tweet2.time]; // ascending return [tweet2.time compare:tweet1.time]; // descending }];*/ if ([results count] &gt; 0) { for (uint i = 0; i &lt; [results count]; i++) { Tweet* tweet = [results objectAtIndex:i]; NSDate* date = Tweet.time; NSLog(@"tweet date: %@", date); } } }]; </code></pre> <p>Can anybody tell me why the NSSortDescriptor isn't working for my fetches?</p> <p>Thanks!</p> <p>-- Update --</p> <p>It seems the NSSortDescriptor works fine when I fetch from the main (parent) managedObjectContext on the main thread without using the performBlock method. This still doesn't help me do sorted fetches on a NSPrivateQueueConcurrencyType managedObjectContext. Creating the NSFetchRequest, NSSortDescriptor and NSPredicate inside the performBlock doesn't fix the problem either.</p>
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