ios - 如何在现有解析对象上重新加载关系

Question

我在数组中有一堆来自 PFFetch 的对象。这些对象具有指向其他对象的链接(指针数组 <-> 指针)。为了限制为我的初始提取发送的数据量，我不想在提取时使用 includeKey 下载所有链接的对象。

一段时间后，我有了这些对象的一个​​子集，我确实想获取这些对象的相关对象和关系。如果我再次获取它们，我会在我的应用程序中复制这些对象(并且可能不必要地通过我在我的应用程序中已有的线路发送对象)

即我希望我的原始数组中的一些对象看起来就像原始提取具有:

[query includeKey:@"relationship"];
[query includeKey@"relationship.secondRelationship"];

设置在原始键上。做这个的最好方式是什么？我想象过 PFObject 上的一些 API，例如:

+(void) fetchIfNeededInBackground:(NSArray*)objects includeKey:(NSString*)key block:...

或

- (void)includeKeyAtNextFetch:(NSString*)key

但是我找不到这样的东西。

Answer 1

您可能正在寻找著名的 containedIn 查询..

这是一个使用 containedIn 解决著名问题“匹配来自 FB 的 friend ”的示例......

+(void)findFBFriendsWhoAreOnSkywall
{
// issue a fb graph api request to get the fbFriend list...

[APP huddie];

[FBRequestConnection
 startForMyFriendsWithCompletionHandler:^(
  FBRequestConnection *connection, id result, NSError *error)
  {
  if (!error)
   {
   // here, the result will contain an array of the user's
   // FB friends, with, the facebook-id in the "data" key

   NSArray *fbfriendObjects = [result objectForKey:@"data"];

   int kountFBFriends = fbfriendObjects.count;

   NSLog(@"myfriends result; count: %d", kountFBFriends);

   // NOW MAKE A SIMPLE ARRAY of the fbId of the friends
   // NOW MAKE A SIMPLE ARRAY of the fbId of the friends
   // NOW MAKE A SIMPLE ARRAY of the fbId of the friends

   NSMutableArray *fbfriendIds =
    [NSMutableArray arrayWithCapacity:kountFBFriends];
   for (NSDictionary *onFBFriendObject in fbfriendObjects)
    [fbfriendIds addObject:[onFBFriendObject objectForKey:@"id"]];

   for (NSString *onef in fbfriendIds)
      NSLog(@"and here they are .. %@", onef);

   // query to find friends whose facebook ids are in that list:
   // USE THAT SIMPLE ARRAY WITH THE MAGIC 'containedIn' call...

   // amazingly easy using the ever-loved containedIn:
   // amazingly easy using the ever-loved containedIn:
   // amazingly easy using the ever-loved containedIn:

   PFQuery *SWUSERSTOADDASFRIENDS = [PFUser query];
   [SWUSERSTOADDASFRIENDS whereKey:@"fbId" containedIn:fbfriendIds];
   [SWUSERSTOADDASFRIENDS findObjectsInBackgroundWithBlock:^
    (NSArray *objects, NSError *error)
    {
    if (error) // problem getting the matching-friends list
     {
     [PFAnalytics .. it al went to hell.];
     NSLog(@"disaster at the last step!  but that's ok");

     [APP.hud hide:YES];
     [backTo literallyGoToMainPage];
     }
    else
     {
     // so all the people in OBJECTS, now make them in to SW friends.

     [PFAnalytics trackEvent:@"FBMatchDone" ...];
     NSLog(@"found this many fb matches ... %d", objects.count);
     [FBMatch actuallyMakeThemFriends:objects];
     [APP.hud hide:YES];
     [FBMatch message .. objects.count showTheseNames:objects];
     }
    }];
   }
  else // problem getting the friend list....
   {
   [PFAnalytics .. problem];

   [APP.hud hide:YES];
   [backTo literallyGoToMainPage];
   }
  }];
}

希望对您有所帮助!