Tracked Property In Array

controllers.application\.js

import Controller from '@ember/controller';
import { tracked } from '@glimmer/tracking';
import { action } from '@ember/object';

export class Room {

  @tracked
  checked = true;
}

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

  rooms = [];

  init() {
    super.init(...arguments);
    this.rooms.pushObject(new Room());
  }

  get hasCheckedRoom() {
    return this.rooms.find((r) => r.checked) !== undefined;
  }


  @action
	checkRooms() {
    this.rooms.forEach((r) => r.checked = true);
  }
  @action
	uncheckRooms() {
    this.rooms.forEach((r) => r.checked = false);
  }
  @action
	clearRooms() {
    this.rooms.clear()
  }

}

templates.application\.hbs

<h1>Welcome to {{this.appName}}</h1>
<br>
{{#if this.hasCheckedRoom}}
  There are checked rooms
{{else}}
  There are no checked rooms
{{/if}}
<br>
There are {{this.rooms.length}} rooms
<br>
<button {{on 'click' this.checkRooms}}>Check All Rooms</button>

<br>
<button {{on 'click' this.uncheckRooms}}>Uncheck All Rooms</button>

<br>
<button {{on 'click' this.clearRooms}}>Clear Rooms Array</button>
<br>
{{outlet}}
<br>
<br>

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"
  }
}