Approach 3 - Event Bus

components.alerts\.js

import Component from '@glimmer/component';
import { action, get } from '@ember/object';
import { tracked } from '@glimmer/tracking';
import { inject as service } from '@ember/service';
import { getOwner } from '@ember/application';

export default class Filters extends Component {
  @tracked filterValue;
  
  constructor() {
    super(...arguments);
    const fullName = 'service:' + get(this.args, 'eventBusName');
    this.eventBusService = getOwner(this).lookup(fullName);
    this.eventBusService.on('filtersUpdated', function(filterValue) {
      this.filterValue = filterValue;
    });
  }
}

components.filters\.js

import Component from '@glimmer/component';
import { action, get } from '@ember/object';
import { tracked } from '@glimmer/tracking';
import { inject as service } from '@ember/service';
import { getOwner } from '@ember/application';

export default class Filters extends Component {
  @tracked filterValue;
  
  constructor() {
    super(...arguments);
    const fullName = 'service:' + get(this.args, 'eventBusName');
    this.eventBusService = getOwner(this).lookup(fullName);
    this.eventBusService.on('filtersUpdated', function(filterValue) {
      debugger;
      
      // 'this' refers to IndexEventBusService's context
      this.filterValue = filterValue;
    });
    this.eventBusService.trigger('filtersUpdated', 1);
  }
  
  @action
  increaseFilter() {
    get(this, 'eventBusService').trigger('filtersUpdated', this.filterValue + 1);
  }
}

controllers.application\.js

import Controller from '@ember/controller';

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

controllers.index\.js

import Controller from '@ember/controller';

export default Controller.extend({
});

controllers.jymbii\.js

import Controller from '@ember/controller';

export default Controller.extend({
});

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('jymbii');
});

export default Router;

routes.index\.js

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

export default Route.extend({
});

routes.jymbii\.js

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

export default Route.extend({
});

services.index-event-bus\.js

import Evented from '@ember/object/evented';
import Service from '@ember/service';
import { tracked } from '@glimmer/tracking';

export default Service.extend(Evented);

services.jymbii-event-bus\.js

import Evented from '@ember/object/evented';
import Service from '@ember/service';

export default Service.extend(Evented);

templates.application\.hbs

<div style="outline: 1px solid black;">
  <h1>Approach 3 - Event Bus</h1>
  {{outlet}}
</div>

templates.components.alerts\.hbs

<div style="outline: 1px solid black; width: 80%; margin: 20px; padding: 10px;">
    <h3>
        Alerts component
    </h3>

    <div>
      Data passed down into the component reflects here
    </div>
    
    {{!--
    <code>
      <div> get dataService() { </div>
      <div> &nbsp; &nbsp; getOwner(this).lookup(this.args.dataServiceName); </div>
      <div> } </div>

      <div> filterValue() { </div>
      <div> &nbsp; &nbsp; get(this, 'dataService').filterValue; </div>
      <div> } </div>
    </code>
    --}}
  
    <div style="color:red;">
      Current Filter Value = {{this.filterValue}}
    </div>
</div>

templates.components.filters\.hbs

<div style="outline: 1px solid black; width: 80%; margin: 20px; padding: 10px">
    <h3>
        Filters component
    </h3>

    <div>
      Actions triggered here are invoked from the dataService
    </div>
    
    {{!-- 
    <code>
      <div> get dataService() { </div>
      <div> &nbsp; &nbsp; getOwner(this).lookup(this.args.dataServiceName); </div>
      <div> } </div>

      <div> constructor() { </div>
      <div> &nbsp; &nbsp; get(this, 'dataService').initializeFilters(1); </div>
      <div> } </div>

      <div> increaseFilter() { </div>
      <div> &nbsp; &nbsp; get(this, 'dataService').increaseFilter(); </div>
      <div> } </div>
    </code>
    --}}

    <div>
      <div style="color:red;">
        Current Filter Value = {{this.filterValue}}
      </div>
      <button onclick={{action "increaseFilter"}}> Click to increase filter value </button>
    </div>
</div>

templates.index\.hbs

<div style="outline: 1px solid black; width: 80%; margin: 20px;padding: 10px;">
  <h2>
    Index route loaded
  </h2>
  
  <div>
  	<p> Route defines the eventBus </p>
    <p> There is no separate state, there is only action-reaction</p>
  </div>

	<h4> Index Template </h4>
  <div> Filters </div>
  <div> &nbsp; &nbsp; @eventBusName='index-event-bus' </div>

  <Filters
    @eventBusName='index-event-bus'
  />
  
  <div> Alerts </div>
  <div> &nbsp; &nbsp; @eventBusName='index-event-bus' </div>
  <Alerts
    @eventBusName='index-event-bus'
  />
</div>

templates.jymbii\.hbs

<div style="outline: 1px solid black; width: 80%; margin: 20px;padding: 10px;">
  <h2>
    JYMMBII route loaded
  </h2>
  
  <div>
  	<p> Route defines the eventBus </p>
    <p> If we want experience-specific state, we can store the state on route </p>
    <p> even then, we should use listeners to update values across components </p>
  </div>

	<h4> Jymbii Template </h4>
  <div> Filters </div>
  <div> &nbsp; &nbsp; @eventBusName='jymbii-event-bus' </div>

  <Filters
    @eventBusName='jymbii-event-bus'
  />
  
  <div> Alerts </div>
  <div> &nbsp; &nbsp; @eventBusName='jymbii-event-bus' </div>
  <Alerts
    @eventBusName='jymbii-event-bus'
  />
</div>

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"
  }
}