0

I have classes named _User & Photo & PhotoJourney. I want to send a Photo to a random user based on some action. In the PhotoJourney class I have a field photo (Pointer to Photo class) and photoSentTo (Pointer to _User class).

My requirement is to get all users excluding those whose photo has been sent.

var PhotoObj = Parse.Object.extend("Photo");
var photo = new PhotoObj();
photo.id = request.params.photoId;

var Query1 = new Parse.Query("User");

var Query2 = new Parse.Query("PhotoJourney");
Query2.select("photoSentTo");
Query2.equalTo("photoID", photo);

Query1.doesNotMatchKeyInQuery("objectId", "photoSentTo", Query2);
Query1.find({
    success: function(results)
    {
    },
    error : function() 
    {
    }
});

If I execute Query2.find(), it gives me the correct result. i.e. a list of users that I want to exclude from _User table, but I am not sure how to do that and which parameters to pass on to doesNotMatchKeyInQuery("","","").

I am quite new to cloud code development. Please correct me if I am doing it wrong.

Thanks in advance.

Improve this question

1 Answer 1

Reset to default
1

Sorry, I actually don't think you can solve this with queries only. I think you need to do it like this:

  1. Get a list of all PhotoJourney objects where photo matches the current photo.
  2. Create a list of user objects by retrieving the photoSentTo object in all PhotoJourney objects (excludeUsers)
  3. Query for all users (allUsers)
  4. As you now have two lists of user objects, filter out the objects from allUsers that exist in excludeUsers

The resulting list is the list you can use for getting a random user.

This is quite a heavy operation if you have lots of users. You should create a cloud code function that does this job on the server and only returns the random user object.

As an alternative, you could create a new field on the Photo object (or create a join table for it) that contains an array of pointers to all the users that have received the Photo. Then, when querying for users, you can exclude users that exist in this list. Or the array could contain only the objectIDs, and you can use that as a constraint in your User query:

userQuery.notContainedIn("objectId", photo.get("sentToUsers")); // Array of objectIds of receivers
Improve this answer
Sign up to request clarification or add additional context in comments.

5 Comments

thanks for your reply. I tried it, but still i am getting all users. response of usersToExcludeQuery query - array of map objects - { "photoSentTo":{ "__type":"Pointer", "className":"_User", "objectId":"cavvHDegMt" }, "objectId":"ZCfiU5wDa1", "createdAt":"2014-05-14T12:39:37.522Z", "updatedAt":"2014-05-14T12:39:37.522Z", "__type":"Object", "className":"PhotoJourney" } response includes fields from PhotoJourney class too. is that the reason users are not excluding?
Try executing only the usersToExcludeQuery and see if that produces any results. If that is empty, no users are excluded...
After executing usersToExcludeQuery. It gives 2 user objects.(I have total 5 users). Response - {"result":[{"photoSentTo":{"__type":"Pointer","className":"_User","objectId":"cavvHDegMt"},"objectId":"ZCfiU5wDa1","createdAt":"2014-05-14T12:39:37.522Z","updatedAt":"2014-05-14T12:39:37.522Z","__type":"Object","className":"PhotoJourney"},{"photoSentTo":{"__type":"Pointer","className":"_User","objectId":"sb5CBKXUAS"},"objectId":"nPrhrj1TTk","createdAt":"2014-05-15T07:04:31.491Z","updatedAt":"2014-05-15T07:04:44.410Z","__type":"Object","className":"PhotoJourney"}]}
Ok, I think I see the problem. Give me a few minutes to think about it.
It worked. thanks for your help. Second way is much better, if we think about the number of users.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.