New Twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  activeItem: undefined,
  
	items: Ember.computed(function() {
		return [
  		{
        title: 'Item 1',
			},
  		{
        title: 'Item 2',
			},
  		{
        title: 'Item 3',
			},      
    ];
	}),
  
  actions: {
  	toggleActiveItem(item) {
    	this.set('activeItem', item);  
    },
    
  },
});

templates.application.hbs

<h1>The app</h1>

{{#each items as |item|}}
	<h3 {{action 'toggleActiveItem' item}}>{{item.title}}</h3>
  
  {{#if (eq item activeItem)}}
  	body
  {{/if}}
{{/each}}

twiddle.json

{
  "version": "0.15.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": true,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.2.2",
    "ember-template-compiler": "3.2.2",
    "ember-testing": "3.2.2"
  },
  "addons": {
    "ember-truth-helpers": "2.0.0"
  }
}