toString()

application.controller.js

var t = { contact: 'John',
          toString: function() {
										return this.contact;
          }
				};


export default Ember.Controller.extend({
	
name: t,
  actions: {
 update() {
		   var name = this.get('name');
       Em.set(name, 'contact', name.contact + '--');
       this.set('name', name);

       console.log(this.get('name'));
      `check your console`
  }}
});

application.template.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{name}}

<button {{action 'update'}}> update name </button>
{{outlet}}
<br>
<br>

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"
  }
}