Computed Update Count

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  _fullName: '',
  fullName: Ember.computed('_fullName', {
    get() {
      return this.get('_fullName');
    },
    set(key, value) {
      if (value !== this.get('_fullName')) {
        this.set('_fullName', value);
        this.set('firstName', value.split(' ')[0]);
      }
      return value;
    }
  }),
  
  _firstName: '',
  firstName: Ember.computed('_firstName', {
    get() {
      return this.get('_firstName');
    },
    set(key, value) {
      if (value !== this.get('_firstName')) {
        this.set('_firstName', value);
        this.set('greeting', `Hello ${value}`);
        this.incrementProperty('count');
      }
      return value;
    }
  }),
  
  greeting: 'Hello ',
  
	count: 0,

});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
Fullname: <input value={{fullName}} oninput={{action (mut fullName) value='target.value'}}>
<br>
Firstname: {{firstName}}
<br>
Greeting: {{greeting}}
<br>
Count: {{count}}

twiddle.json

{
  "version": "0.10.6",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.9.0",
    "ember-data": "2.0.1",
    "ember-template-compiler": "2.9.0",
    "ember-testing": "2.9.0"
  },
  "addons": {}
}