iOS：将现有Core Data数据库迁移到iCloud [英] iOS: Migrating existing Core Data-database into iCloud

问题描述

我在现有应用程序中使用Core Data。现在我想集成iCloud，以便用户可以在他们的iOS设备之间同步他们的内容。为此，我为我的NSPersistentStoreCoordinator写了以下代码（当然，我的代码中填充了占位符）：

I'm using Core Data in an existing application. Now I want to integrate iCloud so that the user can synchronize their contents between their iOS-devices. To do that I've written the following code for my NSPersistentStoreCoordinator (of course the placeholders are filled out in my code):

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {

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

NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"<DB_Name>.sqlite"];

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

NSPersistentStoreCoordinator* psc = persistentStoreCoordinator_;

if (IOS_VERSION_GREATER_THAN_OR_EQUAL_TO(@"5.0")) {
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        NSFileManager *fileManager = [NSFileManager defaultManager];

        // Migrate datamodel
        NSDictionary *options = nil;

        // this needs to match the entitlements and provisioning profile
        NSURL *cloudURL = [fileManager URLForUbiquityContainerIdentifier:@"<App_Identifier>"];
        NSString* coreDataCloudContent = [[cloudURL path] stringByAppendingPathComponent:@"data"];
        if ([coreDataCloudContent length] != 0) {
            // iCloud is available
            cloudURL = [NSURL fileURLWithPath:coreDataCloudContent];

            options = [NSDictionary dictionaryWithObjectsAndKeys:
                       [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
                       [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption,
                       @"<App_Name>.store", NSPersistentStoreUbiquitousContentNameKey,
                       cloudURL, NSPersistentStoreUbiquitousContentURLKey,
                       nil];
        } else {
            // iCloud is not available
            options = [NSDictionary dictionaryWithObjectsAndKeys:
                       [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
                       [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption,
                       nil];
        }

        NSError *error = nil;
        [psc lock];
        if (![psc addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:options error:&error])
        {
            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        }
        [psc unlock];

        dispatch_async(dispatch_get_main_queue(), ^{
            NSLog(@"asynchronously added persistent store!");
            [[NSNotificationCenter defaultCenter] postNotificationName:@"RefetchAllDatabaseData" object:self userInfo:nil];
        });

    });

} else {
    NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                             [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
                             [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption,
                             nil];

    NSError *error = nil;
    if (![persistentStoreCoordinator_ addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:options error:&error])
    {
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    }
}

return persistentStoreCoordinator_;
}

使用该代码，所有新添加的数据记录

With that code all new added data records are synchronized automatically between all iOS-devices, so that works exactly the way it should!

但我想要的也是所有现有的数据记录在所有设备之间同步;这还没有工作。现有记录在应用程序中仍然可用，可以使用，但它们不同步。

But what I want is that also all the existing data records are synced between all devices; that doesn't work yet. The existing records are still available within the app and can be used, but they are not synchronized.

我需要做什么来获取所有现有数据记录同步iCloud吗？我已经尝试了一下方法

What do I need to do to get all the existing data records synced with iCloud too? I've experimented a bit with the method

migratePersistentStore:toURL:options:withType:error:

但未成功。

我非常感谢任何帮助！

推荐答案

查看WWDC 2012会话使用CoreData和iCloud。他们在最后一节中，在种子主题下讨论这个问题。他们还有一些示例代码，您可以从具有示例的网站获取。简而言之，您将必须打开2个持久存储，设置提取大小，然后从源抓取批次，循环并将其添加到新存储，并以批量大小的间隔保存并重置。很简单。

Look up the WWDC 2012 session Using CoreData with iCloud. They discuss this during the final section, under the topic of seeding. They also have some sample code that you can get from the site that has an example. In short, you will have to open 2 persistent stores, set a fetch size, then grab batches from the source, loop through them and add them to the new store, and at batch size intervals, save and reset. Pretty simple.

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