Init value within a component

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName:'Ember Twiddle'
});

application.template.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>

index.route.js

import Ember from 'ember';

export default Ember.Route.extend({
  model () {
    return { 
      id: 11,
      children: [
        { id: 21, name: 'A' },
        { id: 22, name: 'B' },
        { id: 22, name: 'C' }
      ]
    };
  }
});

index.template.hbs

{{my-favs data=model}}

my-favs.component.js

import Ember from 'ember';

export default Ember.Component.extend({
  init () {
    this._super(...arguments);
    // firstObject returns a[0] in Ember
    const firstChild = this.get('data.children.firstObject'); 
    if (firstChild) {
      // if it's an Ember Object then
      // firstChild.set('active', true)
      firstChild.active = true;
    }
  }
});

my-favs.template.hbs

<p>Children:</p>
<ul>
{{#each data.children as |child|}}
<li>
{{input type="checkbox" checked=child.active}}
<span>{{child.name}}</span>
</li>
{{/each}}	
</ul>

{{yield}}

twiddle.json

{
  "version": "0.4.16",
  "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/2.1.0/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.1.0/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.1.0/ember-template-compiler.js"
  }
}