readOnly fun

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  appNameFoo: Ember.computed('appName', {
    get() {
      return this.get('appName') + ' foo';
    }
  }),
  appNameBar: Ember.computed('appName', function() {
    return this.get('appName') + ' bar';
  }).readOnly(),
  
  actions: {
    tryFoo() {
      this.set('appNameFoo', 'noooooo');
    },
    tryBar() {
      this.set('appNameBar', 'noooooo');
    }
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
<h2>{{appNameFoo}} - {{appNameBar}}</h2>
{{outlet}}
<a href="#" {{action 'tryFoo'}}>Try to set foo</a> - <a href="#" {{action 'tryBar'}}>Try to set bar</a>
<br>
<br>

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"
  }
}