Controller singletones

controllers.my-route\.js

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

export default class MyRouteController extends Controller {
  @tracked count = 0;
}

router\.js

import EmberRouter from '@ember/routing/router';
import config from './config/environment';

const Router = EmberRouter.extend({
  location: 'none',
  rootURL: config.rootURL
});

Router.map(function() {
  this.route('my-route')
});

export default Router;

routes.my-route\.js

import Route from '@ember/routing/route';

export default class MyRoute extends Route {
  setupController(controller) {
    controller.count++
  }
}

templates.application\.hbs

<p>
  Visit My Route, then visit Home, then visit My Route again.
  And repeat. Notice that count is increased. 
</p>
<p>
  The Controller for My Route is a singleton that lives for the lifetime of the application.
</p>
<p>
  Try removing <code>tracked</code> to see what happens.
</p>


<LinkTo @route="application">Visit Home</LinkTo> |
<LinkTo @route="my-route">Visit My Route</LinkTo>

<br>
<br>

{{outlet}}

templates.my-route\.hbs

My Route {{this.count}}

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"
  }
}