New Twiddle

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  resetName: false,
  
  name: Ember.computed('resetName', {
    get() {
      return 'defaultName';
    },
    set(key, name) {
      return name;
    }
  }),
  
  actions: {
    setName(value) {
      this.set('name', value);
      this.set('newName', '');
    },
    reset() {
      this.toggleProperty('resetName');
    }
  }
});

application.template.hbs

<p>Name: {{name}}</p>

<p>Set name: {{input value=newName enter='setName'}}</p>

<p>{{resetName}} - <button {{action 'reset'}}>Reset Name</button></p>

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"
  }
}