Question

我一直在寻求让Core Data与iCloud合作，以便可以从多个设备访问人员数据。我一直在关注这个教程（http://timroadley.com/），尽可能地使用我的应用程序，但我遇到了一些问题。

问题1：当应用程序关闭（不仅仅是暂停）并重新打开时，表格中没有显示任何内容，因此以前的数据似乎无法加载

问题2：我不知道它的iCloud或应用程序，但同步更改需要很长时间。我在一台设备上进行了更改，在另一台设备上显示需要2-3分钟

任何人都可以帮我解决这两个问题

此代码位于我的AppDelegate

中

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

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
    {
    if((__persistentStoreCoordinator != nil)) {
        return __persistentStoreCoordinator;
    }

    __persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel: [self managedObjectModel]];
    NSPersistentStoreCoordinator *psc = __persistentStoreCoordinator;

    // Set up iCloud in another thread:

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

        // ** Note: if you adapt this code for your own use, you MUST change this variable:
        NSString *iCloudEnabledAppID = @"MF4HVVX5DS.Desbrina.Medicine-Tracker";

        // ** Note: if you adapt this code for your own use, you should change this variable:
        NSString *dataFileName = @"Medicine-Tracker.sqlite";

        // ** Note: For basic usage you shouldn't need to change anything else

        NSString *iCloudDataDirectoryName = @"Data.nosync";
        NSString *iCloudLogsDirectoryName = @"Logs";
        NSFileManager *fileManager = [NSFileManager defaultManager];
        NSURL *localStore = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:dataFileName];
        NSURL *iCloud = [fileManager URLForUbiquityContainerIdentifier:nil];

        if (iCloud) {

            NSLog(@"iCloud is working");

            NSURL *iCloudLogsPath = [NSURL fileURLWithPath:[[iCloud path] stringByAppendingPathComponent:iCloudLogsDirectoryName]];

            NSLog(@"iCloudEnabledAppID = %@",iCloudEnabledAppID);
            NSLog(@"dataFileName = %@", dataFileName);
            NSLog(@"iCloudDataDirectoryName = %@", iCloudDataDirectoryName);
            NSLog(@"iCloudLogsDirectoryName = %@", iCloudLogsDirectoryName);
            NSLog(@"iCloud = %@", iCloud);
            NSLog(@"iCloudLogsPath = %@", iCloudLogsPath);

            if([fileManager fileExistsAtPath:[[iCloud path] stringByAppendingPathComponent:iCloudDataDirectoryName]] == NO) {
                NSError *fileSystemError;
                [fileManager createDirectoryAtPath:[[iCloud path] stringByAppendingPathComponent:iCloudDataDirectoryName]
                       withIntermediateDirectories:YES
                                        attributes:nil
                                             error:&fileSystemError];
                if(fileSystemError != nil) {
                    NSLog(@"Error creating database directory %@", fileSystemError);
                }
            }

            NSString *iCloudData = [[[iCloud path]
                                     stringByAppendingPathComponent:iCloudDataDirectoryName]
                                    stringByAppendingPathComponent:dataFileName];

            NSLog(@"iCloudData = %@", iCloudData);

            NSMutableDictionary *options = [NSMutableDictionary dictionary];
            [options setObject:[NSNumber numberWithBool:YES] forKey:NSMigratePersistentStoresAutomaticallyOption];
            [options setObject:[NSNumber numberWithBool:YES] forKey:NSInferMappingModelAutomaticallyOption];
            [options setObject:iCloudEnabledAppID            forKey:NSPersistentStoreUbiquitousContentNameKey];
            [options setObject:iCloudLogsPath                forKey:NSPersistentStoreUbiquitousContentURLKey];

            [psc lock];

            [psc addPersistentStoreWithType:NSSQLiteStoreType
                              configuration:nil
                                        URL:[NSURL fileURLWithPath:iCloudData]
                                    options:options
                                      error:nil];

            [psc unlock];
        }
        else {
            NSLog(@"iCloud is NOT working - using a local store");
            NSMutableDictionary *options = [NSMutableDictionary dictionary];
            [options setObject:[NSNumber numberWithBool:YES] forKey:NSMigratePersistentStoresAutomaticallyOption];
            [options setObject:[NSNumber numberWithBool:YES] forKey:NSInferMappingModelAutomaticallyOption];

            [psc lock];

            [psc addPersistentStoreWithType:NSSQLiteStoreType
                              configuration:nil
                                        URL:localStore
                                    options:options
                                      error:nil];
            [psc unlock];

        }

        dispatch_async(dispatch_get_main_queue(), ^{
            [[NSNotificationCenter defaultCenter] postNotificationName:@"SomethingChanged" object:self userInfo:nil];
        });
    });

    return __persistentStoreCoordinator;
}

- (NSManagedObjectContext *)managedObjectContext {

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

    NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];

    if (coordinator != nil) {
        NSManagedObjectContext* moc = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];

        [moc performBlockAndWait:^{
            [moc setPersistentStoreCoordinator: coordinator];
            [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(mergeChangesFrom_iCloud:) name:NSPersistentStoreDidImportUbiquitousContentChangesNotification object:coordinator];
        }];
        __managedObjectContext = moc;
    }

    return __managedObjectContext;
}

- (void)mergeChangesFrom_iCloud:(NSNotification *)notification {

    NSLog(@"Merging in changes from iCloud...");

    NSManagedObjectContext* moc = [self managedObjectContext];

    [moc performBlock:^{

        [moc mergeChangesFromContextDidSaveNotification:notification];

        NSNotification* refreshNotification = [NSNotification notificationWithName:@"SomethingChanged"
                                                                            object:self
                                                                          userInfo:[notification userInfo]];

        [[NSNotificationCenter defaultCenter] postNotification:refreshNotification];
    }];
}

，这是在主视图控制器

中

- (void)reloadFetchedResults:(NSNotification*)note {
    NSLog(@"Underlying data changed ... refreshing!");
    [self fetchedResultsController];
    NSLog(@"%@", note.object);
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    self.navigationItem.leftBarButtonItem = self.editButtonItem;

    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(reloadFetchedResults:)
                                                 name:@"SomethingChanged"
                                               object:[[UIApplication sharedApplication] delegate]];
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.

    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

Answer 1

问题1：当应用程序关闭（不仅仅是暂停）并重新打开时，表格中没有显示任何内容，因此以前的数据似乎无法加载

检查是否将所有数据保存到托管对象上下文。这不应该是核心数据问题

问题2：我不知道它的iCloud或应用程序，但同步更改需要很长时间。我在一台设备上进行了更改，在另一台设备上显示需要2-3分钟

2-3分钟真的很好。有时需要数小时才能使数据处于完全同步状态。至少我半年前经历过这个。

请记住，iCloud不适合在多个设备上同时使用。它提供了最终的一致性。

Answer 2

在你的例子中

： NSURL * iCloud = [fileManager URLForUbiquityContainerIdentifier：nil]; 用你的 NSString * iCloudEnabledAppID = @“MF4HVVX5DS.Desbrina.Medicine-Tracker”; as URLForUbiquityContainerIdentifier

它应该是这样的：

NSURL * iCloud = [fileManager URLForUbiquityContainerIdentifier：iCloudEnabledAppID];

iCloud中的iOS核心数据存储与其他设备同步

2 个答案: