async

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: Ember.computed.alias('model.firstObject.bar.foo.name'),
  bar: Ember.computed.alias('model.firstObject.bar'),
  test: Ember.computed('bar', function () { 
    return this.get('bar.foo').then(function (d) {
      console.log(d.get('name'))
    })
  })
});

application.route.js

import Ember from 'ember';

export default Ember.Route.extend({
  beforeModel() {
  	const foo = this.store.createRecord('foo', {
    	name: 'foo'
    })
    const bar = this.store.createRecord('bar', { foo })
    const baz = this.store.createRecord('baz', { bar })
    // return Ember.RSVP.all([foo, bar, baz])
  },
  model () {
  	return this.store.findAll('baz')//.then(baz => {
    	//return baz.get('firstObject.bar').then(bar => {
      //  return bar.get('foo')
      //})
    //})
  }
});

application.template.hbs

<h1>Welcome to {{appName}}</h1>
<br>
{{foo}}
<br>
{{log test}}
<br>
<br>

models.bar.js

import DS from 'ember-data';

export default DS.Model.extend({
  foo: DS.belongsTo()
});

models.baz.js

import DS from 'ember-data';

export default DS.Model.extend({
  bar: DS.belongsTo()
});

models.foo.js

import DS from 'ember-data';

export default DS.Model.extend({
  name: DS.attr()
});

twiddle.json

{
  "version": "0.4.17",
  "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/2.2.0/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.2.0/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.2.0/ember-template-compiler.js"
  }
}