Service - Array observer sample

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  cart:Ember.inject.service(),    
 actions:{
  addEntry(){
    this.get('cart').addEntry();
  }
 }
});

services.cart.js

import Ember from 'ember';

export default Ember.Service.extend({
  bucket:['initial'],
  addEntry(){
    console.log('entry added');
    this.get('bucket').pushObject('added');
  },
  bucketListener: Ember.observer('bucket.@each',function(){
   Ember.run.once(this,'bucketChange');
  }),
  bucketChange(){
    console.log('bucketChange');
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<button {{action "addEntry" }}> add entry </button>
<br>
{{outlet}}
<br>
<br>

twiddle.json

{
  "version": "0.10.3",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.7.0",
    "ember-data": "2.7.0",
    "ember-template-compiler": "2.7.0"
  },
  "addons": {}
}