iOS: Migrating existing Core Data-database into iCloud - ios

Question

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_;
}
With that code all new added data records are synchronized automatically between all iOS-devices, so that works exactly the way it should!
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.
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:
but without any success.
I'm very grateful for any help!

Answer 1

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.