Trampolined Properties

controllers.application.js

import Ember from 'ember';
let t = 0;
export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  theKey: 'one',
  
  one: 1,
  two: 2,
  
  message: Ember.computed.alias('messageTrampoline.message'),
  
  init() {
    this._super(...arguments);
    
		Ember.defineProperty(this, 'messageTrampoline', Ember.computed('theKey', function() {
      let key = this.get('theKey');
    	return Ember.Object.extend({
        message: Ember.computed('parent.'+key, function() {
          let thing = this.get('parent.'+key);
          return `Hi, ${thing}`;
        })
      }).create({parent: this});
    }));
  },
  
  actions: {
    bump(key) {
      this.incrementProperty(key);
    },
    toggle() {
      t++;
      if (t % 2 === 0) {
				this.set('theKey', 'one');
      } else {
        this.set('theKey', 'two');
      }
    }
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{message}}
<br>
<button {{action 'bump' 'one'}}>One</button>
<button {{action 'bump' 'two'}}>Two</button>
<button {{action 'toggle'}}>Toggle</button>
<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"
  }
}