New Twiddle

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName:'Nested Routes - Loading'
});

application.template.hbs

<h1>{{appName}}</h1>

{{#link-to 'index'}}Go to root{{/link-to}}
{{#link-to 'foo'}}Go to foo{{/link-to}}
{{#link-to 'foo.bar'}}Go to foo.bar{{/link-to}}
{{#link-to 'foo.bar.baz'}}Go to foo.bar.baz{{/link-to}}

{{outlet}}

foo.bar.baz.loading.template.hbs

<h2>This is the BAZ loading template!</h2>

foo.bar.baz.route.js

import Ember from 'ember';

export default Ember.Route.extend({
  model () {
    return new Ember.RSVP.Promise(function(resolve/*, reject*/) {
      Ember.run.later(function() {
        resolve( Ember.A([]) );
      }, 2000);
    });
  }
});

foo.bar.baz.template.hbs

<h2>BAZ</h2>
{{outlet}}

foo.bar.loading.template.hbs

<h2>This is the BAR loading template!</h2>

foo.bar.route.js

import Ember from 'ember';

export default Ember.Route.extend({
  model () {
    return new Ember.RSVP.Promise(function(resolve/*, reject*/) {
      Ember.run.later(function() {
        resolve( Ember.A([]) );
      }, 1500);
    });
  }
});

foo.bar.template.hbs

<h2>BAR</h2>
{{outlet}}

foo.loading.template.hbs

<h2>This is the FOO loading template!</h2>

foo.route.js

import Ember from 'ember';

export default Ember.Route.extend({
  model () {
    return Ember.RSVP.Promise.resolve( Ember.A([]) );
  }
});

foo.template.hbs

<h2>FOO</h2>
{{outlet}}

router.js

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

var Router = Ember.Router.extend({
  location: config.locationType
});

Router.map(function() {
  this.route('foo', function() {
    this.route('bar', function() {
      this.route('baz');
    });
  });
});

export default Router;

twiddle.json

{
  "version": "0.4.11",
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/1.13.9/ember.debug.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/1.13.9/ember-template-compiler.js"
  }
}