New Twiddle

controllers.application\.js

import Controller from '@ember/controller';
import EmberObject from '@ember/object';

import { action } from '@ember/object';
import { readOnly } from '@ember/object/computed';


class Buzz extends EmberObject {
  
  bar = 0;

  _foo = 0;
  @readOnly('_foo') foo;

  @action
  increment(prop) {
    this.incrementProperty(prop);
  }
}

export default class ApplicationController extends Controller {
  appName = 'Ember Twiddle';

  buzz = Buzz.create();

  get bar() {
    return this.buzz.bar;
  }

  get foo() {
    return this.buzz.foo;
  }

  @action
  increment() {
    this.buzz.increment('_foo');
    this.buzz.increment('bar');
  }
}

templates.application\.hbs

<h1>Tracking</h1>

<ul>
  <li>Bar direct: {{this.buzz.bar}}</li>
  <li>Bar via getter: {{this.bar}}</li>
  <li>Foo direct: {{this.buzz.foo}}</li>
  <li>Foo via getter: {{this.foo}}</li>
</ul>

<button {{on 'click' this.increment}}>Increment</button>

twiddle\.json

{
  "version": "0.17.1",
  "EmberENV": {
    "FEATURES": {},
    "_TEMPLATE_ONLY_GLIMMER_COMPONENTS": false,
    "_APPLICATION_TEMPLATE_WRAPPER": true,
    "_JQUERY_INTEGRATION": true
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.js",
    "ember": "3.18.1",
    "ember-template-compiler": "3.18.1",
    "ember-testing": "3.18.1"
  },
  "addons": {
    "@glimmer/component": "1.0.0"
  }
}