Ember data nested URL

application_adapter.js.erb

export default DS.ActiveModelAdapter.extend({
  namespace: 'api/v<%= Rails.application.config.ember.api_version %>',

  buildNestedURL: function(parents, type) {
    var _this = this;
    var url = Ember.makeArray(parents).map(function(model) {
      return _this.buildURL(model.constructor.typeKey, model.get('id'));
    });

    url.push(this.pathForType(type));

    return url.join('/');
  }
});

submission_adapter.js

import ApplicationAdapter from "./application";

export default ApplicationAdapter.extend({
  createRecord: function(store, type, record) {
    var data = {};
    var serializer = store.serializerFor(type.typeKey);
    var challenge = record.get('challenge');
    var url = this.buildNestedURL(challenge, type.typeKey);

    serializer.serializeIntoHash(data, type, record, { includeId: true });

    return this.ajax(url, "POST", { data: data });
  
});