computed example

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  a: Ember.Object.create({ b: 3 }),
  
  c: Ember.computed('a', function() {
    return this.get('a.b');
  }),
  
  d: Ember.computed('a', 'a.b', function() {
    return this.get('a.b');
  }),
    
  actions: {
    updateA() {
      this.set('a', Ember.Object.create({
        b: 5
      }));
    },
    
    updateB() {
      this.set('a.b', 7);
    }
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
<h1>The value of 'a.b' is:</h1>
computed('a', ...: {{c}}
<br>
computed('a', 'a.b', ...: {{d}}
<br>
<button {{action "updateA"}}>set a</button>
<br>
<button {{action "updateB"}}>set a.b</button>
{{outlet}}
<br>
<br>

twiddle.json

{
  "version": "0.13.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.16.2",
    "ember-template-compiler": "2.16.2",
    "ember-testing": "2.16.2"
  },
  "addons": {
    "ember-data": "2.16.3"
  }
}