New Twiddle

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  val: Ember.computed({
  	get: function () {
    	return 'INITIAL VALUE';  
    },
    set: function (property, value) {
    	return value;  
    }
  }),
  
  somethingElse: null,
  
  actions: {
  	onChange: function (prop, val) {
    	this.set(prop, val);  
    }
  }
});

controllers.application.js

import Ember from 'ember';

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

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>
{{my-component}}

templates.components.my-component.hbs

Val: {{val}}
<br />
SomethingElse: {{somethingElse}}
<br />
<br />
<button {{action 'onChange' 'val' 'test'}}>Change</button> <br />
<button {{action 'onChange' 'somethingElse' 'test123'}}>Change</button>

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}