指针所在的PFQuery

Question

我的数据库中有两个表：

Posts
    -    content
    -    user (pointer)
Likes
    -    post (pointer)
    -    user (pointer)

我正在计算用户有多少帖子“喜欢”--但唯一的问题是有些帖子并不存在，因为它们已经被删除了。所以我基本上想做的就是在帖子存在的地方获取所有的“赞”。

我现在的查询是这样的：

PFQuery *query = [PFQuery queryWithClassName:@"Likes"];
[query whereKey:@"user" isEqualTo:self.user];
[query includeKey:@"post"];
[query includeKey:@"post.owner"];

Answer 1

您可以使用-whereKey:matchesKey:inQuery:方法创建第二个针对Post类的查询：

PFQuery *likesQuery = [PFQuery queryWithClassName:@"Likes"];
[query whereKey:@"user" isEqualTo:self.user];
// don't have to include these since this is a subquery
//[query includeKey:@"post"];
//[query includeKey:@"post.owner"];

PFQuery *postsQuery = [PFQuery queryWithClassName:@"Posts"];
[query whereKey:@"objectId" matchesKey:"post" inQuery:likesQuery];

然后，postsQuery将能够给你现有的和用户喜欢的帖子的数量。