New Twiddle

helpers.url-for.js

import Ember from 'ember';

export default Ember.Helper.extend({
  router: Ember.computed(function() {
    return Ember.getOwner(this).lookup('router:main');
  }),

  compute([routeName, ...routeParams]) {
    let router = this.get('router');

    return Ember.isEmpty(routeParams) ? 
      router.generate(routeName) :
    	router.generate(routeName, routeParams[0]);
  }
});

router.js

import Ember from 'ember';
import config from './config/environment';

const Router = Ember.Router.extend({
  location: 'none'
});

Router.map(function() {
    this.route('about');
    this.route('posts', function() {
    this.route('post', {path: '/:post_id'});
  });
});

export default Router;

templates.application.hbs

<h3>Urls:</h3>
<ul>
<li>{{url-for 'about'}}</li>
<li>{{url-for 'posts'}}</li>
<li>{{url-for 'posts.post' 2}}</li>
</ul>
<br>
<br>

twiddle.json

{
  "version": "0.7.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.4.3/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.4.3/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.4.3/ember-template-compiler.js"
  }
}