Ember Data nested join relation computed function

computed-many-through-async.js

import { createSortableArray } from './sortable-array-proxy';

const { get, set } = Ember;

/****
 * TODO: If need sorting, add sort logic
*****/
export default function computedManyThroughAsync(joinRelationAttr, nestedRelationAttr, sortProperties, sortAscending = true) {
  return Ember.computed(joinRelationAttr, function() {
    var joinRelationPromise = get(this, joinRelationAttr);

    if (joinRelationPromise) {
      return DS.PromiseArray.create({
        promise: joinRelationPromise.then(function(joinModels) {
          if (joinModels) {
            var promiseArray = [];

            joinModels.forEach(function(joinModel) {
              var nestedRelationPromise = get(joinModel, nestedRelationAttr);

              if (nestedRelationPromise) {
                promiseArray.push(get(nestedRelationPromise));
              }
            });

            return Ember.RSVP.all(promiseArray);
        });
      });
    }
  });
}

foo.js

import DS from 'ember-data';
import computedManyThroughAsync from '../utils/computed-many-through-async'; /* say ^^^ is stored here */

/*******
 * say a join model exists called 'foo-bar' like so
 * export default DS.Model.extend({
 *   bar: DS.belongsTo('bar'),
 *   foo: DS.belongsTo('foo')
 * });
 *******/


export default DS.Model.extend({
  fooBars: DS.hasMany('foo-bar'),
  bars: computedManyThroughAsync('fooBars', 'foo')
});

/* Now  foo.get('bars') returns a PromiseArray of nested bar models. */