NSMetadataQuery notification block not called

Hello all

I am having problems using NSMetadataQuery to check cloud states. Consider the code snippet below (originally inspired by the code posted in

http://stackoverflow.com/questions/22112700/how-do-i-create-a-nsmetadataquery-and-get-results-on-a-background-thread):

NSMetadataQuery *query = [[NSMetadataQuery alloc] init];

void (^notificationBlock)(NSNotification __strong *notification) = ^(NSNotification __strong *notification) {

NSLog(@"entering notification block");

};

[query enableUpdates];

NSURL *url = [[[NSFileManager defaultManager] URLForUbiquityContainerIdentifier:nil] URLByAppendingPathComponent: @"Documents"];

NSPredicate *metadataPredicate = [NSPredicate predicateWithFormat:@"%K BEGINSWITH %@", NSMetadataItemPathKey, url.path];

query.notificationBatchingInterval = 1.0;

query.searchScopes = [NSArray arrayWithObject:NSMetadataQueryUbiquitousDataScope];

query.predicate = metadataPredicate;

NSOperationQueue* nsQueue = [NSOperationQueue new];

[[NSNotificationCenter defaultCenter]

addObserverForName:NSMetadataQueryDidFinishGatheringNotification

object:query

queue:nsQueue

usingBlock:notificationBlock

];

[query startQuery];

[NSThread sleepForTimeInterval: 1000.0f];

My expectation would be that the notification block gets called by another thread while the main thread is sleeping. Instead the block is never called. Any help is greatly appreciated.