Why is UbiquityContainer nil if user not logged into iCloud?

Question

I would like to use the UbiquityContainer in order to have an iCloud backup of the coredata. However if I am not logged into the iCloud on the simulator the ubContainer below remains nil.

-(void)addSqliteStoreToPersistentStoreCoordinator:(NSPersistentStoreCoordinator *)psc{
    NSError *error = nil;
    NSFileManager *fm = [NSFileManager defaultManager];
    NSURL *ubContainer = [fm URLForUbiquityContainerIdentifier:nil]; // Why nil???????
    NSURL *storeURL = [ubContainer URLByAppendingPathComponent:@"f11Remote.sqlite"];
    NSMutableDictionary *options = [NSMutableDictionary dictionary];
    [options setObject:[NSNumber numberWithBool:YES] forKey:NSMigratePersistentStoresAutomaticallyOption];
    [options setObject:[NSNumber numberWithBool:YES] forKey:NSInferMappingModelAutomaticallyOption];
    [options setObject:[NSDictionary dictionaryWithObjectsAndKeys:@"FULL", @"synchronous", nil] forKey:NSSQLitePragmasOption];
    [options setObject:@"f11iCloudStore" forKey:NSPersistentStoreUbiquitousContentNameKey];
    [options setValue:ubContainer forKey:NSPersistentStoreUbiquitousContentURLKey];
    sqliteStore = [psc addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:options error:&error];
    if (!sqliteStore)
        [NSException raise:@"FTDatastore: Couldn't open the local SQLite database." format:@"Reason: %@", [error localizedDescription]];
}

I was expecting an offline version of it to work in the meanwhile and behave like core data, until the user logs into the iCloud. What can be done?

If the user isn't logged in then there is no ubiquity container. That's why it is `nil`. The user could log into one of several possible iClouds account. Each will have its own container. — rmaddy, May 27 '15 at 22:15
"What can be done?" What can be done about _what_? This works as expected. What's the problem? Okay, it's a horrible architecture: you have to deal with a persistent store in multiple places. But hey, that's iCloud. — matt, May 27 '15 at 22:32
@rmaddy so I have to rollout a normal coredata container in case the user is logged out and migrate it to iCloud whenever he logs back in? — Houman, May 27 '15 at 22:38

score 1 · Answer 1 · answered May 28 '15 at 08:16

You need a fallback store in case the user did not activate iCloud.

NSURL *storeDirectory = [[NSFileManager defaultManager] 
                        URLForUbiquityContainerIdentifier:nil];

Why nil?

If you specify nil for this parameter, this method returns the first container listed in the com.apple.developer.ubiquity-container-identifiers entitlement array.

If the resulting URL is nil, iCloud is likely disabled. You have to provide an alternative URL.

if (!storeDirectory) {
   storeDirectory = [self applicationDocumentsDirectory]; // implement yourself
   NSLog(@"Falling back to local store.");
}

Thank you for explaining it so well. +1 I agree with implementing a fallback to local store if iCloud is disabled. However what do I do, if the user has been iCloud and suddenly decides to logout. The local fallback store would be empty, and he won't be seeing his data. Maybe I should always migrate the iCloud data also to a local data store, for cases like this. — Houman, May 28 '15 at 08:22

Why is UbiquityContainer nil if user not logged into iCloud?

1 Answers1