Ember Route Multiple Model Mixin

my-route.js

import Ember from 'ember';
import RouteRequiredModelsMixin from '../mixins/route-required-models';

export default Ember.Route.extend(RouteRequiredModelsMixin, {
  // Hash values from here will be directly set on the controller
  requiredModels(resolvedModel, transition) {
    return {
      books: this.store.findAll('books')
    }
  },
  
  // for looking up up parent route requiredModels use
  // this.requiredModelsFor('my-route'), just like this.modelFor()
});

route-required-models.js

import Ember from 'ember';

const { RSVP, getOwner } = Ember;

export default Ember.Mixin.create({
  /**
   * Use this method to define additional models your route requires
   *
   * @example
   * return {
   *    groups: this.store.findAll('group'),
   *    ...
   *  }
   *
   * @public
   * @return {Object}
   */

  requiredModels(/*model, transition*/) {
    return {};
  },

  /**
   * Use this to lookup parent route additional models
   *
   * @public
   * @param  {String} name
   * @return {Mixed}
   */

  requiredModelsFor(name) {
    let route = getOwner(this).lookup(`route:${name}`);
    return route && route.get('__resolvedRequiredModels');
  },

  /**
   * This method initialized RSVP for the hash returned from requiredModels method
   *
   * @private
   * @param  {Model} model
   * @param  {Transition} transition
   * @return {Promise}
   */

  _initializeRequiredModels(model, transition) {
    let hash = this.requiredModels(model, transition);
    if (Object.keys(hash).length > 0) {
      return new RSVP.hash(hash).then((resolvedModels) => {
        this.set('__resolvedRequiredModels', resolvedModels);
      });
    }
  },

  /**
   * Initialize additional models query to API and wait for it
   *
   * @public
   * @Ember
   * @param  {Model} model
   * @param  {Tansition} transition
   * @return {Promise}
   */

  afterModel(model, transition) {
    return this._initializeRequiredModels(model, transition);
  },

  /**
   * Finally when setupController is called, setup models from hash to controller
   *
   * @public
   * @Ember
   * @param  {Controller} controller
   */

  setupController(controller) {
    this._super(...arguments);
    let models = this.get('__resolvedRequiredModels');
    if (models) {
      controller.setProperties(models);
    }
  }
});