Question

I’m finishing my Core Data app ans I started my final testing.

Everyfing works fine, except one thing, that happens randomly and I can’t reproduce it.

Here is the log (with NSZombieEnabled):

2011-07-03 20:27:53.144 MYAPP[1882:707] -[__NSCFType controllerWillChangeContent:]: unrecognized selector sent to instance 0x4a4c490
2011-07-03 20:27:53.149 MYAPP[1882:707] Serious application error.  Exception was caught during Core Data change processing.  This is usually a bug within an observer of NSManagedObjectContextObjectsDidChangeNotification.  -[__NSCFType controllerWillChangeContent:]: unrecognized selector sent to instance 0x4a4c490 with userInfo (null)
2011-07-03 20:27:53.165 MYAPP[1882:707] CoreAnimation: ignoring exception: -[__NSCFType controllerWillChangeContent:]: unrecognized selector sent to instance 0x4a4c490

It crashes here:

NSManagedObjectContext *context = [(AppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext]; // IT'S OK
NSManagedObject *newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:@"Kontrahent" inManagedObjectContext:context]; // IT'S OK
for(NSString *key in kontrahent) [newManagedObject setValue:[kontrahent valueForKey:key] forKey:key];  // IT'S OK
NSError *error = nil;
if (![context save:&error]) {  // IT'S NOT OK
    NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    abort();
}

My action hierarchy:

1. Open application
2. Open my 'root' list (with NSFetchedResultsController, entity: "Faktura")
3. Tap 'Add' button
4. In my 'Add' view controller I create another object (entity: "Kontrahent")
5. I try to add it to database
6. It crashes / It doesn't.

SCHEME:

        +---[moc save:]---> Faktury (my root class)
        |                        ↓
        +-----delegate-- FakturaCreator <---[moc save:]--+  <--- HERE IT CRASHES
                                 ↓                       |
                         KontrahentCreator ---delegate---+

I know that it’s connected with NSFetchedResultsController and [moc save:]. But I can’t locate my problem, because it crashes when it wants. Sometimes it works, sometimes it crashes. If you know something abou this problem, please help me 🙂

---

IF YOU NEED MORE CODE…

NSFetchedResultsController stuff (Faktury.m)

#pragma mark - Fetched results controller

- (NSFetchedResultsController *)fetchedResultsController {
    
    if (__fetchedResultsController != nil) return __fetchedResultsController;
    
    // Setup the table
    
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Faktura" inManagedObjectContext:self.managedObjectContext];
    [fetchRequest setEntity:entity];
    
    // Setup the sort descriptors
    
    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"NumerFV" ascending:YES];
    NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
    [fetchRequest setSortDescriptors:sortDescriptors];
    
    // Create the fetched results controller
    
    NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:@"Root"];
    aFetchedResultsController.delegate = self;
    self.fetchedResultsController = aFetchedResultsController;
    
    [aFetchedResultsController release];
    [fetchRequest release];
    [sortDescriptor release];
    [sortDescriptors release];
    
    NSError *error = nil;
    if (![self.fetchedResultsController performFetch:&error]) {
        
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Błąd Krytyczny" message:@"Wystąpił nieznany błąd przy zmienianiu zawartości w bazie danych. Dla dobra twoich danych prosimy niezwłocznie wyjść z aplikacji i spróbować ponownie." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
        [alert show];
        [alert release];
        
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }
    
    return __fetchedResultsController;
}    

#pragma mark - Fetched results controller delegate

- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
    [tableView beginUpdates];
}

- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
           atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {
    switch(type) {
        case NSFetchedResultsChangeInsert:
            [tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;
            
        case NSFetchedResultsChangeDelete:
            [tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}

- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath
     forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath {
    
    if([[[controller sections] objectAtIndex:0] numberOfObjects] == 0) {
        emptySectionView.hidden = NO;
        UIBarButtonItem *editBtn = [[UIBarButtonItem alloc] initWithTitle:@"Edytuj" style:UIBarButtonItemStyleBordered target:self action:@selector(toogleEditing)];
        editBtn.enabled = NO;
        [self.navigationItem setLeftBarButtonItem:editBtn animated:NO];
        [editBtn release];
    } else {
        emptySectionView.hidden = YES;
        self.navigationItem.leftBarButtonItem.enabled = YES;
    }
    
    UITableView *table = tableView;
    
    switch(type) {
            
        case NSFetchedResultsChangeInsert:
            [table insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;
            
        case NSFetchedResultsChangeDelete:
            [table deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationLeft];
            break;
            
        case NSFetchedResultsChangeUpdate:
            [self configureCell:(KSTableViewCell *)[table cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
            break;
            
        case NSFetchedResultsChangeMove:
            [table deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
            [table insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}

- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
    [tableView endUpdates];
}

When I tap the add button (Faktury.m)

- (void)add:(id)sender {
    FakturaCreator *form = [[FakturaCreator alloc] init];
    form.hidesBottomBarWhenPushed = YES;
    form.delegate = self;
    form.managedObjectContext = self.managedObjectContext;
    [self.navigationController pushViewController:form animated:YES];
    [form release];
}

Answer 1

OK, I located my problem. I have a ‘KontrahentPicker’ and it has NSFetchedResultsController too. But this UIViewController was presented as modalViewController. I pucked my Kontrahent and modal was dismissed and released. But NSFRC‘s delegate was still active.

I solved my problem by putting

self.fetchedResultsController.delegate = nil;

in -dealloc method.