Conditional Classname

components.my-component.js

import Component from 'ember-component';
import computed from 'ember-computed';
import get from 'ember-metal/get';

export default Component.extend({
  classNameBindings: ['mobileClass'],
  
  mobileClass: computed('media.isMobile', {
    get() {
      if (get(this, 'media.isMobile')) {
        return 'column sixteen';
      } else {
        return 'column trisector';
      }
    }
  })
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  media: {
    isMobile: true
  }
});

templates.application.hbs

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

{{my-component media=media}}

templates.components.my-component.hbs

{{yield}}

<div class="{{mobileClass}}"></div>

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"
  }
}