Create relation between two classes to allow data query

Question

Updated, response to suggested answer provided, awaiting response before bounty award.

Using Parse.com and JavaScript SDK.

I appear unable to solve this, so will put it out to bounty. For the bounty I'd like a code example/solution that solve the problem and that I can learn from.

The below code saves an object to the "mybadges" class. I'd like to have either a pointer or relation in the "FriendRequest" class connected to the mybadges class. Meaning that when I click on the pointer or relation in "FriendRequests" it returns all of the objects uploaded into the myBadges class. I then want to be able to access this data via a query.

Using Parse.com and JavaScript SDK.

Parse.initialize("xxx", "xxx");

                var user = Parse.User.current();

                var MyBadges = Parse.Object.extend("myBadges");
                var userbadges = new MyBadges();

                var Friends = Parse.Object.extend("FriendRequest");
                var friends = new Friends();

                //var Badges = Parse.Object.extend("myBadges");


                //var Badges = Parse.Object.extend("myBadges");

                    $(document).ready(function () {

                    $("#send").click(function () {

                        var badgeselected = $('#badgeselect .go').attr("src");
                        userbadges.set("BadgeName", badgeselected);
                        userbadges.set("uploadedBy", user);
                        //friends.set("status");
                        //friends.save();

                        userbadges.save(null, {
                            success: function (results) {
                        // The object was saved successfully.

                        friends.relation('Friends').add(userbadges);
                        //friends.save();
                        console.log(user);

                        //location.reload();
                    },
                    error: function (contact, error) {
                        // The save failed.
                        // error is a Parse.Error with an error code and description.
                        alert("Error: " + error.code + " " + error.message);
                    }
                });
                    });
                });


                                    $(document).ready(function() {
                    $('.go').css('cursor', 'pointer');
            $('.go').click(function(e) { // Button which will activate our modal
                $(this).width(100).height(100).appendTo('#badgeselect');


                $('#modal').reveal({ // The item which will be opened with reveal
                    animation: 'fade',                   // fade, fadeAndPop, none
                    animationspeed: 600,                       // how fast animtions are
                    closeonbackgroundclick: true,              // if you click background will modal close?
                    dismissmodalclass: 'close'    // the class of a button or element that will close an open modal


                });
                return false;
               });
        });

Answer 1

To create a one-to-many relationship there are a couple of options:

• Use "back reference" links, i.e. add a friendRequest pointer to your myBadges class (only supports one-to-many)
• Add a column of type Array (good for small lists, supports many-to-many)
• Add a column of type Relation (use queries to navigate, supports many-to-many)
• Create a custom class to hold the relationships (if you have other data about each join, supports many-to-many) The simplest option is using the Array column, in JavaScript you just use a normal array that contains myBadges instances and assign it to a property of your parent class.

Note: In my examples below, I'm going to change the case of call classes to UpperCamel singular (myBadges -> MyBadge) and all properties/column names to lowerCamel (BadgeName -> badgeName) for consistency, and I suggest you do the same.

Examples:

Common code assumed in the below:

var FriendRequest = Parse.Object.extend("FriendRequest");
var MyBadge = Parse.Object.extend("MyBadge");
var friendRequest = /* some FriendRequest you've loaded */

---

Option 1 - back-reference

Adding new badge to a friend request:

// MyBadge.friendRequest: Pointer (to FriendRequest)
var myBadge = new MyBadge();
myBadge.set({
    badgeName: someStringVariable,
    uploadedBy: someUserObject,
    friendRequest: friendRequest
});
myBadge.save();

Getting badges for a friend request:

var badgesQuery = new Parse.Query(MyBadge);
badgesQuery.equalTo('friendRequest', friendRequest);
badgesQuery.find({
    success: function(badges) {
        // use badges as needed...
    }
});

Showing MyBadge rows for FriendRequest parent in Data Browser:

Get the objectId of a FriendRequest row, then on the view for MyBadge add a filter on the friendRequest column and paste the ID.

---

Option 2 - Array

Adding new badge to a friend request:

// FriendRequest.badges: Array (of MyBadge)

// 2-step process, first create and save the MyBadge instance
var myBadge = new MyBadge();
myBadge.set({
    badgeName: someStringVariable,
    uploadedBy: someUserObject
});
myBadge.save()
// step 2 (using chaining here) attach the saved badge to the friend request
.then(function() {
    friendRequest.badges.addUnique(myBadge);
    // return promise to allow further chaining
    return friendRequest.save();
});

Getting badges for a friend request:

// just include them when querying for FriendRequest objects
friendRequestQuery.include('badges');

Showing MyBadge rows for FriendRequest parent in Data Browser:

No support for this, you'll need to create your own solution.

---

Option 3 - Relation

Adding new badge:

// FriendRequest.badges: Relation (of MyBadge)

// 2-step process, first create and save the MyBadge instance
var myBadge = new MyBadge();
myBadge.set({
    badgeName: someStringVariable,
    uploadedBy: someUserObject
});
myBadge.save()
// step 2 (using chaining here) attach the saved badge to the friend request
.then(function() {
    var badgesRelation = friendRequest.relation('badges');
    badgesRelation.add(myBadge);
    // return promise to allow further chaining
    return friendRequest.save();
});

Getting badges for a friend request:

// query the relation
var badgesRelation = friendRequest.relation('badges');
var badgesQuery = badgesRelation.query();
// apply any filters as you would for any normal Parse.Query()
// ...
// use find() or any other query method
badgesQuery.find({
    success: function(badges) {
        // use array of badges...
    }
})

Showing MyBadge rows for FriendRequest parent in Data Browser:

Double-click on a value in the badges column.

---

Option 4 - custom join class

This isn't really suitable for your use-case, so I'm not going to provide a sample here.