Model Ref Self

controllers.application.js

import Ember from 'ember';

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

controllers.home.js

import Ember from 'ember';

export default Ember.Controller.extend({
  myObject: null,
  
  actions: {
  
  	selectedSomething(index) {
    	console.log(index);
      let newParent = this.get('items').objectAt(index);
      this.set('myObject.parent', newParent);
    }
  
  }
});

models.my-model.js

import Model from "ember-data/model";
import attr from "ember-data/attr";
import { belongsTo, hasMany } from "ember-data/relationships";

export default Model.extend({
  label: attr('string'),
  parent: attr()
});

router.js

import Ember from 'ember';

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

Router.map(function() {
      this.route('home', {path: '/'});
});

export default Router;

routes.home.js

import Ember from 'ember';

export default Ember.Route.extend({
  setupController: function(controller) {
    controller.set('myObject', this.store.createRecord('my-model', {label: 'myObject'}));
    controller.set('items', [
      this.store.createRecord('my-model', {label: 'parentOne'}),
      this.store.createRecord('my-model', {label: 'parentTwo'})
    ]);
  }
});

templates.application.hbs

Welcome
{{outlet}}

templates.home.hbs

<select onchange={{action "selectedSomething" value="target.selectedIndex"}}>
{{#each items as |item|}}
   <option>{{item.label}}</option>
{{/each}}
</select>
<hr>
Controller: {{myObject.label}}<br>
Selected Parent: {{myObject.parent}}<br>
Parent's Label: {{myObject.parent.label}}

twiddle.json

{
  "version": "0.8.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.5.1",
    "ember-data": "2.5.2",
    "ember-template-compiler": "2.5.1"
  }
}