New Twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

models.person.js

import Model from 'ember-data/model';
import attr from 'ember-data/attr';
import { belongsTo, hasMany } from 'ember-data/relationships';

export default Model.extend({
  something: attr('string')
});

routes.application.js

import Ember from 'ember';
import RSVP from 'rsvp';

export default Ember.Route.extend({
  model() {
    return new RSVP.Promise(resolve => {
      resolve([this.store.createRecord('person', {
        something: 'hi'
      })]);
    });
  },
  afterModel(model) {
    new RSVP.Promise(resolve => {
      Ember.run.later(() => {
        for (const person of model) {
          person.set('arbitraryProperty', 'woot');
          // person.arbitraryProperty = 'woot';
        }
      }, 3000);
    });
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>
{{#each model as |person|}}
	{{person.arbitraryProperty}}
{{/each}}

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.4.2"
  }
}