New Twiddle

controllers.application.js

import Ember from 'ember';
import computed from 'ember-macro-helpers/computed';

const Foo = Ember.ArrayProxy.extend({
  content: [],
  
  expected: computed('content.@each.qux', content => JSON.stringify({ content })),

  actual: computed('@each.qux', content => JSON.stringify({ content }))
});

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  foo: Foo.create(),
  
  actions: {
    addItem(value) {
      this.get('foo').pushObject({ qux: value });
    }
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>

<div>Expected: {{foo.expected}}</div>

<div>Actual: {{foo.actual}}</div>

<input type="text" onchange={{action 'addItem' value='target.value'}}>

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1",
    "ember-macro-helpers": "0.15.0"
  }
}