+entityForName: nil ist nicht eine juristische NSManagedObjectContext parameter der Suche für die Entität name 'Scores'

Ok, also, nicht, dass die app delegieren, sollte in der core-data-stack, aber in dem moment, in dem Sie es tun, und die Instanz, die Inhaberin des core-data-stack benötigt zum erstellen des stack - im moment ist nichts zu tun.

Alles, was Sie haben, ist

@synthesize managedObjectContext = _managedObjectContext;
@synthesize managedObjectModel = _managedObjectModel;
@synthesize persistentStoreCoordinator = _persistentStoreCoordinator;

welche erstellt nur einige accessor-Methoden. Nichts setzt diese Instanz-Variablen.

Sollten Sie einige code wie der unten behemoth, siehe auch diese.

- (NSManagedObjectContext *)managedObjectContext {

    if (_managedObjectContext != nil) {
        return _managedObjectContext;
    }

    NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
    if (coordinator != nil) {
        _managedObjectContext = [NSManagedObjectContext new];
        [_managedObjectContext setPersistentStoreCoordinator: coordinator];
    }
    return _managedObjectContext;
}

/**
 Returns the managed object model for the application.
 If the model doesn't already exist, it is created by merging all of the models found in the application bundle.
 */
- (NSManagedObjectModel *)managedObjectModel {

    if (_managedObjectModel != nil) {
        return _managedObjectModel;
    }
    _managedObjectModel = [NSManagedObjectModel mergedModelFromBundles:nil];
    return _managedObjectModel;
}

/**
 Returns the URL to the application's documents directory.
 */
- (NSURL *)applicationDocumentsDirectory
{
    return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}

/**
 Returns the persistent store coordinator for the application.
 If the coordinator doesn't already exist, it is created and the application's store added to it.
 */
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {

    if (_persistentStoreCoordinator != nil) {
        return _persistentStoreCoordinator;
    }

    //copy the default store (with a pre-populated data) into our Documents folder
    //
    NSString *documentsStorePath =
        [[[self applicationDocumentsDirectory] path] stringByAppendingPathComponent:@"Recipes.sqlite"];

    //if the expected store doesn't exist, copy the default store
    if (![[NSFileManager defaultManager] fileExistsAtPath:documentsStorePath]) {
        NSString *defaultStorePath = [[NSBundle mainBundle] pathForResource:@"Recipes" ofType:@"sqlite"];
        if (defaultStorePath) {
            [[NSFileManager defaultManager] copyItemAtPath:defaultStorePath toPath:documentsStorePath error:NULL];
        }
    }

    _persistentStoreCoordinator =
        [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];

    //add the default store to our coordinator
    NSError *error;
    NSURL *defaultStoreURL = [NSURL fileURLWithPath:documentsStorePath];
   if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType
                                                  configuration:nil
                                                            URL:defaultStoreURL
                                                        options:nil
                                                          error:&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.

         Typical reasons for an error here include:
         * The persistent store is not accessible
         * The schema for the persistent store is incompatible with current managed object model
         Check the error message to determine what the actual problem was.
         */
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }

    //setup and add the user's store to our coordinator
    NSURL *userStoreURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"UserRecipes.sqlite"];
    if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType
                                                                     configuration:nil
                                                                               URL:userStoreURL
                                                                           options:nil
                                                                             error:&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.

         Typical reasons for an error here include:
         * The persistent store is not accessible
         * The schema for the persistent store is incompatible with current managed object model
         Check the error message to determine what the actual problem was.
         */
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }

    return _persistentStoreCoordinator;
}