Private Binding

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  service: Ember.inject.service('thing-service'),
  
  color: Ember.computed.alias('service.color'),
  appName:'Ember Twiddle',
  
  actions: {
    changeColor() {
      if (this.get('color') === 'blue') {
        console.log('setting to red');
        this.get('service').setColor('red');
      }
      else {
        console.log('setting to blue');
        this.get('service').setColor('blue');
      }
    }
  }
});

application.template.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
<p>{{color}}</p>
<button {{action 'changeColor'}}>Change Color</button>

services.thing-service.js

import Ember from 'ember';

var obj = Ember.Object.extend({
  internalValue: 'blue'
});

export default Ember.Service.extend({
	init() {
    var self = this;
    var internalVal = obj.create();
		this.color = internalVal.get('internalValue');
    
    internalVal.addObserver('internalValue', function(sender) {
      console.log('internalValue changed ' + sender.get('internalValue'));
    	self.set('color', sender.get('internalValue'));
    });
    
    this.setColor = function(colorName) {
    	internalVal.set('internalValue', colorName);
    };
	}
});

twiddle.json

{
  "version": "0.4.10",
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/1.13.9/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/1.13.11/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/1.13.9/ember-template-compiler.js"
  }
}