oneWay WAT

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName:'Ember Twiddle',
  name: "ten",
  
  tennison: Ember.Object.create({
  	name: 'tennison',
    friend: Ember.Object.create({
    	name: 'will'
    })
  }),
  
  nickName: Ember.computed.oneWay('tennison.friend.name')
});

application.template.hbs

<p>Nick Name: {{nickName}}</p>

Change Friend Nick: <input value={{nickName}} oninput={{action (mut nickName) value="target.value"}}>
<br>

twiddle.json

{
  "version": "0.4.17",
  "EmberENV": {
    "FEATURES": {}
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.2.0",
    "ember-data": "2.2.0",
    "ember-template-compiler": "2.2.0"
  }
}