Stackoverflow Question#43204082

components.first-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  myService: Ember.inject.service(),
  
  actions: {
    incrementTotal() {
      let total = this.get('myService').getTotal();
      total = Ember.isBlank(total) ? 0 : total;
      this.get('myService').setTotal(total+1);
    }
  }
});

components.second-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  myService: Ember.inject.service(),
		
  // Below will also work:
  //serviceTotal: Ember.computed.alias('myService.total'),
  serviceTotal: Ember.computed('myService.total', function(){
    return this.get('myService').getTotal();
  })
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

services.my-service.js

import Ember from 'ember';

export default Ember.Service.extend({
     total: '',

    setTotal(total) {
        this.set('total', total);
    },
    getTotal(){
        return this.get('total');
    }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
{{first-component}}
<br>
<br>
{{second-component}}
<br>
<br>

templates.components.first-component.hbs

{{yield}}
This is the component to change service's total!
<button onclick={{action 'incrementTotal'}}>Change Total</button>

templates.components.second-component.hbs

{{yield}}
This is the component where change in total is reflected!
{{serviceTotal}}

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}