New Twiddle

controllers.application.js

import Ember from 'ember';

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

templates.application.hbs

{{test-component id="one"}}
{{test-component id="two"}}

test-component.component.js

import Ember from 'ember';

export default Ember.Component.extend({
  id: undefined,
  
  sharedObjectReference: { // delibrately shared across instances!
    selectedId: undefined,
  },
  
  isSelected: Ember.computed('sharedObjectReference.selectedId', 'id', function() {
    return this.get('sharedObjectReference.selectedId') === this.get('id');
  }),
  
  click() {
    this.set('sharedObjectReference.selectedId', this.get('id'));
  }
});

test-component.template.hbs

I am component: {{id}}
{{#if isSelected}} * {{/if}}

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": true,
    "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"
  }
}