Core Data is not persisting data between app launches

Question

I have a app that is using core data. The Core Data stack (the context, object graph, persistent store coordinator, and the persistent store) is being created, and I am able to use it without issue. The problem is that the saved data is not persisting, can someone help me with what I am doing wrong? Here is where I create the Core Data stack.

- (void)initializeCoreDataStack
{
    NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"Favorites"
                                              withExtension:@"momd"];
    if (!modelURL)
        NSLog(@"MODEL URL NOT INITIALIZED");

    NSManagedObjectModel *mom = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
    if (!mom)
        NSLog(@"OBJECT MODEL NOT CREATED");

    NSPersistentStoreCoordinator * psc = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:mom];
    if (!psc)
        NSLog(@"PERSISTENT STORE COORDINATOR NOT CREATED");

    NSManagedObjectContext *moc = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
    [moc setPersistentStoreCoordinator:psc];
    self.managedObjectContext = moc;

    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    dispatch_async(queue, ^{
       NSArray *directory = [[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory
                                                               inDomains:NSUserDomainMask];
        NSURL *storeUrl = [directory lastObject];
        storeUrl = [storeUrl URLByAppendingPathComponent:@"Favorites.sqlite"];

        NSError *error = nil;
        NSPersistentStore *store = [psc addPersistentStoreWithType:NSSQLiteStoreType
                                                     configuration:nil
                                                               URL:storeUrl
                                                           options:nil
                                                             error:&error];
        if (!store)
        {
            NSLog(@"ERROR CREATING STORE: %@ %@", error.localizedDescription, error.domain);
            // present error to user
        }
        else
        {
            dispatch_sync(dispatch_get_main_queue(), ^{
                // do something once the stack is finished being created
                NSLog(@"persistent store created");
            });
        }
    });
}

Jason McDermott Jason McDermott · Accepted Answer · 2014-01-30T02:14:17

You have to save core data explicitly, otherwise it won't persist. Not hard to solve, though.

In your controller implementation file (e.g. coreDataViewController.m), call this function when you want to save changes to core data

// add this call, whenever you want to save data
// e.g. responding to a UIButton event
[self saveCoreDataContext];

- (void)saveCoreDataContext
{
    NSError *error = nil;
    NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
    if (managedObjectContext != nil) {
        if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {
            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
            abort();
        }
    }
}

Core Data is not persisting data between app launches

4 Answers