New Twiddle

components.calendar-day\.js

import Component from '@glimmer/component';
import { action, computed } from '@ember/object';
import { inject as service } from '@ember/service';

export default class extends Component {
  @service alarms;
  
  get currentAlarmsKey1() {
    console.log('computed key 1');
  	return this.alarms.alarms['key1'];
  }
  
  get currentAlarmsKey2() {
    console.log('computed key 2');
  	return this.alarms.alarms['key2'];
  }
  
  @action
  add(key) {
    this.alarms.add(key);
  }
}

controllers.application\.js

import Controller from '@ember/controller';

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

services.alarms\.js

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

export default class AlarmsService extends Service {
  alarms = {'key1': [{set: true}], 'key2': []};
  add(key) {
    console.log('adding ' + key);
    this.alarms[key] = this.alarms[key] || [];
    this.alarms[key].pushObject({set: true});
  }
}

styles.app\.css

body {
  margin: 12px 16px;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 12pt;
}

.box {
  border: 1px solid red;
}

a {
  color: blue;
}

templates.application\.hbs

<h1>Welcome to {{this.appName}}</h1>
<br>
<br>
{{outlet}}
<Calendar-day />
<br>
<br>

templates.components.calendar-day\.hbs

<div class="box">
<h5>Alarms for key 1</h5>
<ul>
{{#each currentAlarmsKey1 as |alarm index|}}
   <li>Alarm {{index}}</li>
{{/each}}
</ul>
<a {{on 'click' (fn this.add 'key1')}}>Add to key 1</a>
</div>

<div class="box">
<h5>Alarms for key 2</h5>
<ul>
{{#each currentAlarmsKey2 as |alarm index|}}
   <li>Alarm {{index}}</li>
{{/each}}
</ul>
<a {{on 'click' (fn this.add 'key2')}}>Add to key 2</a>
</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"
  }
}