New Twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  _foo: 0,
  bar: 0,
  
//   foo: Ember.computed({
//     get() {
//       return ++this._foo; 
//     }
//   }).volatile(),
  
  get foo() {
    return ++this._foo;
  },
  
  baz: Ember.computed('bar', {
    get() {
      return `${this.foo} ${this.bar}`;
    }
  }),
  
  actions: {
    updateBar() {
      this.set('bar', this.bar + 1);
    }
  }
});

templates.application.hbs

{{baz}}

<button {{action 'updateBar'}}>Foo</button>

twiddle.json

{
  "version": "0.15.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.2.2",
    "ember-template-compiler": "3.2.2",
    "ember-testing": "3.2.2"
  },
  "addons": {
    "ember-data": "3.2.0"
  }
}