使用CoreData获取XMPPFramework中的名单

Question

我想从xmppRosters获得名单。有两种方法：

1. 发送iq

   - (void)queryRoster {
       NSXMLElement *query = [NSXMLElement elementWithName:@"query" xmlns:@"jabber:iq:roster"];
       NSXMLElement *iq = [NSXMLElement elementWithName:@"iq"];
       XMPPJID *myJID = self.stream.myJID;
       [iq addAttributeWithName:@"from" stringValue:@"zhaoyan@127.0.01"];
       [iq addAttributeWithName:@"to" stringValue:@"127.0.0.1"];
       [iq addAttributeWithName:@"id" stringValue:@"1993"];
       [iq addAttributeWithName:@"type" stringValue:@"get"];
       [iq addChild:query];
       [self.stream sendElement:iq];
   }
   

2. 获取CoreData的名单，但我没有得到正确的结果，我非常沮丧。

   - (void)getRosters
   {
       self.xmppRosterStorage = [[XMPPRosterCoreDataStorage alloc]init];
       self.roster = [[XMPPRoster alloc]initWithRosterStorage:_xmppRosterStorage];
       _roster.autoFetchRoster = YES;
       _roster.autoAcceptKnownPresenceSubscriptionRequests= YES;
   
       [_roster fetchRoster];
       [_roster activate:self.stream];
       self.context = _xmppRosterStorage.mainThreadManagedObjectContext;
   
   
       NSFetchRequest * request = [[NSFetchRequest alloc]initWithEntityName:NSStringFromClass([XMPPUserCoreDataStorageObject class])];
       NSString * useinfo = @"zhaoyan@127.0.0.";
       NSPredicate *predicate =[NSPredicate predicateWithFormat:@"streamBareJidStr=%@",useinfo];
       request.predicate = predicate;
       NSSortDescriptor * sortD = [NSSortDescriptor sortDescriptorWithKey:@"displayName" ascending:YES];
       [request setSortDescriptors:@[sortD]];
   
       self.resultsController = [[NSFetchedResultsController alloc]initWithFetchRequest:request managedObjectContext:self.context sectionNameKeyPath:nil cacheName:nil];
       // 执行fetch
       NSError * error = nil;
       [self.resultsController performFetch:&error];
       self.resultsController.delegate = self;
   
       if (error)
       {
           NSLog(@"error coredata");
       }
       else
       {
           NSLog(@"fetch array : %@",[self.resultsController fetchedObjects]);
       }