New Twiddle

components.child\.js

import Component from '@glimmer/component';
import { tracked } from '@glimmer/tracking';
import { get } from '@ember/object';

export default class extends Component {
	get isCountSet() {
    return this.args.object.count;
  }
  
  	get isTestSet() {
    return this.args.test;
  }
}

components.parent\.js

import Component from '@glimmer/component';
import { tracked } from '@glimmer/tracking';
import { action, set } from '@ember/object';

export default class extends Component {
  @tracked test = false;
  constructor() {
  	super(...arguments);
    
    this.objects = [{id: 1, name: "Alex"}, {id: 2, name: "Vasile"}]
  }
  
  @action
  addCount() {
    console.log('count set');
    this.test = true;
    this.objects.forEach((object) => {
      set(object, "count", Math.random());
    });
  }
}

controllers.application\.js

import Controller from '@ember/controller';

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

templates.application\.hbs

<h1>Welcome to {{this.appName}}</h1>
<br>
<br>
<Parent />
<br>
<br>

templates.components.child\.hbs

<div>Hi, I'm the child for {{@object.name}}</div>
<small>Count is {{@object.count}}</small>
<div>Is count set?
  {{#if isCountSet}}
  	true
    {{else}}
    false
  {{/if}}
</div>
<div>Is TEST set?
  {{#if isTestSet}}
  	true
    {{else}}
    false
  {{/if}}
</div>
<br/>

templates.components.parent\.hbs

<div>Hi, I'm the parent</div>
<buton {{on "click" this.addCount}}>Click to set random counts</buton>
<br/>
<br/>
{{#each objects as |object|}}
	<Child @object={{object}} @test={{test}} />
{{/each}}

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"
  }
}