accessing service array

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName:'Ember Twiddle',
  messenger: Ember.inject.service('my-service'),
  i: 4,
  actions: {
    addMessage() {
      this.get('messenger.messages').addObject(this.get('i'));
      this.incrementProperty('i');
    }
  }
});

application.template.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{my-component}}
<br>
<button onclick={{action "addMessage"}}>Add message {{i}}</button>
<br>

my-component.component.js

import Ember from 'ember';

export default Ember.Component.extend({
  messenger: Ember.inject.service('my-service'),
  messages: Ember.computed.readOnly('messenger.messages')
});

my-component.template.hbs

<ul>
{{#each messages as |m|}}
  <li>{{m}}</li>
 {{/each}}
</ul>

my-service.service.js

import Ember from 'ember';

export default Ember.Service.extend({
  messages: [1, 2, 3, 4]
});

twiddle.json

{
  "version": "0.4.17",
  "EmberENV": {
    "FEATURES": {}
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.2.0/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.2.0/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.2.0/ember-template-compiler.js"
  }
}