iOS- parse framework nested query

Question

I have two tables TrendingUsers and Follow. Functionality required is like fetch users from TrendingUsers table and offer to follow, provided fetched user is not from user's follow list. If user is already get followed then skip.

Follow table has columns follower and leader.

PFQuery *followTableQuery = [PFQuery queryWithClassName:@"Follow"];
[followTableQuery whereKey:@"follower" equalTo:[PFUser currentUser] ];
[followTableQuery whereKey:@"leader" equalTo:@"fetchedUserObject" ];
[followTableQuery findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
    if (!error) {
        if (objects.count) {
          //if following objects array will have single object
        }
        else
        {
            //not following to @"fetchedUserObject" user
        }

    }
  }
 ];

This will confirm me that currentUser is following @"fetchedUserObject" user or not. Now I want to integrate this to the TrendingUsers table query to fetch only such users that currentUser is not following.

eschanet · Accepted Answer · 2015-09-04 09:26:04Z

2

You can simply use nested queries, the docs from Parse are usually a good starting point. Here is a sample code, from what I understood from your question, this should do the trick.

//This is our current user
PFUser *user = [PFUser currentUser];

//The first query, querying for all the follow objects from the current user
PFQuery *followingQuery = [PFQuery queryWithClassName:@"Follow"];
[followingQuery whereKey:@"follower" equalTo:user];

//Now we query for the actual trending users, but we do not want the query to return the users (who are in the @"leader" key) that have been found by the first query
PFQuery *trendingQuery = [PFQuery queryWithClassName:@"TrendingUsers"];
[trendingQuery whereKey:@"objectId" notEqualTo:user.objectId]; //don't return the current user
[trendingQuery whereKey:@"objectId" doesNotMatchKey:@"leader" inQuery:followingQuery]; //I'm supposing that @"leader" is containing the objectId of the specific user that is part of the follow object with the current user
[trendingQuery setLimit:1000];
[trendingQuery findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error)
{
    //...
}];

I may have not understood your data structure completely, so you may have to exchange one or more keys in the above code, but basically, this is how you would do this.

edited Sep 4, 2015 at 9:26

answered Aug 14, 2015 at 16:26

eschanet

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1 Comment

Preetam Jadakar Over a year ago

perfect..looking for the same !

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