ios - 核心数据不是在应用程序启动之间保留数据

Question

我有一个正在使用核心数据的应用程序。正在创建核心数据堆栈(上下文、对象图、持久存储协调器和持久存储)，我可以毫无问题地使用它。问题是保存的数据不持久，有人可以帮助我解决我做错的事情吗？这是我创建核心数据堆栈的地方。

- (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");
            });
        }
    });
}

Answer 1

您必须显式保存核心数据，否则它不会持久。不过解决起来并不难。

在 Controller 实现文件(例如 coreDataViewController.m)中，当您想要保存对核心数据的更改时调用此函数

// 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();
        }
    }
}