title: CloudKit subscription with "CONTAINS" predicate
body: <p>I am trying to setup a CloudKit subscription based on testing membership in an array.</p>
  
  <p>The code I'm using to create the subscription is as follows:</p>
  
  <pre><code>NSPredicate *predicate = [NSPredicate predicateWithFormat:@"users CONTAINS %@", userID];
  CKSubscription *itemSubscription = [[CKSubscription alloc] initWithRecordType:@"foo"
                                                                  predicate:predicate
                                                                    options:CKSubscriptionOptionsFiresOnRecordCreation|CKSubscriptionOptionsFiresOnRecordUpdate];
  
  CKNotificationInfo *notificationInfo = [[CKNotificationInfo alloc] init];
  [notificationInfo setAlertLocalizationKey:@"Record notification"];
  [notificationInfo setShouldBadge:YES];
  
  [itemSubscription setNotificationInfo:notificationInfo];
  
  [database saveSubscription:itemSubscription completionHandler:^(CKSubscription *subscription, NSError *error) {
      NSLog(@"Error: %@, Subscription: %@", error, subscription);
  }];
  </code></pre>
  
  <p>The log shows that the subscription is created successfully, however when I test by adding or changing a record via the CloudKit admin console I never get a notification on device.</p>
  
  <p>I am able to receive notifications for subscriptions with other kinds of predicates (I've tested with a simple true predicate, and one that tests equality against a string field), so I know I have the notification code setup correctly.</p>
  
  <p>I've also verified that my predicate listed above works when used in a fetch records query, so I know the predicate is setup correctly for the record type I have in CloudKit.</p>
  
  <p>Has anyone been able to get subscription notifications with a predicate that tests for membership in an array?</p>