child model

components.child-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  answersDidChange: Ember.on('init', Ember.observer('answers', 	   function() {
    // some side effect of salutation changing
    console.log('answers changed to ' + this.get('answers'));
  })),
  didInsertElement: function() {
  	console.log('answers ' + this.get('answers'));
    let array = JSON.parse(this.get('answers'));
    array.push(4);
    this.set('answers', JSON.stringify(array));
    
  }
});

components.parent-component.js

import Ember from 'ember';

export default Ember.Component.extend({
});

controllers.application.js

import Ember from 'ember';

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

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{parent-component}}
<br>
<br>

templates.components.child-component.hbs

{{answers}}

templates.components.parent-component.hbs

parent : {{child-component answers='[1,2,3]'}}

twiddle.json

{
  "version": "0.10.6",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.9.0",
    "ember-data": "2.9.0",
    "ember-template-compiler": "2.9.0",
    "ember-testing": "2.9.0"
  },
  "addons": {}
}