Computed properties in components

components.sensor-item.js

import Ember from 'ember';

export default Ember.Component.extend({
  messages: [],
  alertAmount: Ember.computed('messages.length', function() {
  	return this.get('messages.length');
  }),
  
  init() {
  	this._super(...arguments);
    setTimeout(() => {
    	if(this.get('sensor.enabled')) {
      	this.get('messages').pushObject('foo');
      }
    }, 1000);
  }
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  model: [
    Ember.Object.create({ enabled: true, description: 'living room'}),
    Ember.Object.create({ enabled: false, description: 'bedroom'})
  ]
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{#each model as |sensor|}}
	{{sensor-item sensor=sensor}}
{{/each}}
<br>
<br>

templates.components.sensor-item.hbs

<span>{{sensor.description}} - Activity {{alertAmount}} </span>

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"
  }
}