Comment puis-je résoudre NSInternalInconsistencyException', la raison: '+entityForName: fail rapport

Mon code ressemble à ça:

NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
        NSEntityDescription *entity = [[self.fetchedResultsController fetchRequest] entity];
        NSManagedObject *newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context];

        //If appropriate, configure the new managed object.
        [newManagedObject setValue:[NSDate date] forKey:@"date"];

           //Save the context.
            NSError *error = nil;
            if (![context save:&error]) { 
                NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
                abort();
        }

dans .h fichier d'en-tête, j'ai ceci:

@interface TretiViewController : UIViewController <NSFetchedResultsControllerDelegate> {

 NSFetchedResultsController *fetchedResultsController_;
    NSManagedObjectContext *managedObjectContext_;

 //private NSString *accountID;
}


@property (nonatomic, retain) NSManagedObjectContext *managedObjectContext;
@property (nonatomic, retain) NSFetchedResultsController *fetchedResultsController;

Il doit enregistrer des données à l'aide de base de données, mais il tombe sur l'erreur:

NavTest[1372:207] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '+entityForName: could not locate an NSManagedObjectModel for entity name 'Obrat''
*** Call stack at first throw:
(
0   CoreFoundation                      0x00f92be9 __exceptionPreprocess + 185
1   libobjc.A.dylib                     0x010e75c2 objc_exception_throw + 47
2   CoreData                            0x00cbf45b +[NSEntityDescription entityForName:inManagedObjectContext:] + 187
3   NavTest                             0x0000c210 -[TretiViewController fetchedResultsController] + 187
4   NavTest                             0x00007a76 -[TretiViewController ukazObrat0] + 38
5   UIKit                               0x002c4a6e -[UIApplication sendAction:to:from:forEvent:] + 119
6   UIKit                               0x003531b5 -[UIControl sendAction:to:forEvent:] + 67
7   UIKit                               0x00355647 -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 527
8   UIKit                               0x00354438 -[UIControl touchesBegan:withEvent:] + 277
9   UIKit                               0x0054f987 _UIGestureRecognizerSortAndSendDelayedTouches + 3609
10  UIKit                               0x005500fc _UIGestureRecognizerUpdateObserver + 927
11  CoreFoundation                      0x00f73fbb __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 27
12  CoreFoundation                      0x00f090e7 __CFRunLoopDoObservers + 295
13  CoreFoundation                      0x00ed1bd7 __CFRunLoopRun + 1575
14  CoreFoundation                      0x00ed1240 CFRunLoopRunSpecific + 208
15  CoreFoundation                      0x00ed1161 CFRunLoopRunInMode + 97
16  GraphicsServices                    0x018c7268 GSEventRunModal + 217
17  GraphicsServices                    0x018c732d GSEventRun + 115
18  UIKit                               0x002d342e UIApplicationMain + 1160
19  NavTest                             0x00002594 main + 102
20  NavTest                             0x00002525 start + 53
)

dans NavTest.xcdatamodel j'ai deux entytis Obrta avec attributes et Evet qui est par défaut.

- (NSFetchedResultsController *)fetchedResultsController {
if (fetchedResultsController_ != nil) {
return fetchedResultsController_;
}
// Set up the fetched results controller.
//Create the fetch request for the entity.
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
//Edit the entity name as appropriate.
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Obrat" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
//Set the batch size to a suitable number.
[fetchRequest setFetchBatchSize:20];
//Edit the sort key as appropriate.
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"date" ascending:NO];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
//Edit the section name key path and cache name if appropriate.
//nil for section name key path means "no sections".
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 (![fetchedResultsController_ performFetch:&error]) {
//Replace this implementation with code to handle the error appropriately.
//abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button.
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
return fetchedResultsController_;
}    

Ce qui me manque?