Stackoverflow Question #42827268 - modified

controllers.application.js

import Ember from 'ember';

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

controllers.index.js

import Ember from 'ember';

export default Ember.Controller.extend({
  myService: Ember.inject.service(),
  
  actions: {
    onbuttonclick() {
      this.get('myService').performToggling();
    }
  }
});

router.js

import Ember from 'ember';
import config from './config/environment';

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

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

export default Router;

routes.baseRoute.js

import Ember from 'ember';

export default Ember.Route.extend({
  performLogging(message) {
    console.log(`${this.get('identifier')}--${message}`);
  },
  
  activate() {
    this.performLogging('activate');
  },
  
  afterModel(){
    this.performLogging('afterModel');
  },
  
  deactivate(){
    this.performLogging('deactivate');
  },
  
  beforeModel() {
    this.performLogging('beforeModel');
  },
  
  model() {
    this.performLogging('model');
  },
  
  actions: {
    didTransition() {
    	this.performLogging('didTransition');
  	}
  }

});

routes.index.js

import BaseRoute from './baseRoute';

export default BaseRoute.extend({
  identifier: 'index',
  myService: Ember.inject.service(),
  
  init() {
    this.get('myService');
  },
  
  propertyObserver: Ember.observer('myService.property', function(){
    console.log('I am observing @index.js');
    this.doAction();
  }),
  
  doAction() {
    console.log('@index dummy-action');
  },
  actions: {
    dummyAction() {
      this.doAction();
    }
  }
});

routes.my-route.js

import BaseRoute from './baseRoute';

export default BaseRoute.extend({
  identifier: 'my-route',
	myService: Ember.inject.service(),

  actions: {
    didTransition() {
    	this.performLogging('didTransition');
      this.get('myService').performToggling();
  	}
  }
});

services.my-service.js

import Ember from 'ember';

export default Ember.Service.extend({
  property: true,
  
  performToggling() {
    this.toggleProperty('property');
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}


<br>
<br>

templates.index.hbs

{{#link-to 'my-route'}}Go to my-route{{/link-to}}
<br>
<button {{action 'onbuttonclick'}}>Update service property @my-controller</button>

templates.my-route.hbs

Now @my-route but see the console log!!!
Observer @index route is still working as expected!!!
The reason is; it is singleton!!!

twiddle.json

{
  "version": "0.11.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.11.0",
    "ember-data": "2.11.0",
    "ember-template-compiler": "2.11.0",
    "ember-testing": "2.11.0"
  },
  "addons": {}
}