Observing Global State

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  globalState: Ember.inject.service(),
  foo: Ember.computed('globalState.state', function() {
    console.log('foo');
    this.globalState.state;
    return 'Foo';
  }),
  bar: Ember.computed('foo', function() {
    console.log('bar');
    this.foo;
    return 'Bar';
  }),
  didRender() {
    this._super(...arguments);
    
    console.log('did render');
  }
});

services.global-state.js

import Ember from 'ember';

export default Ember.Service.extend({
  init() {
    this._super(...arguments);
    setInterval(() => {
      console.log('set state');
      this.set('state', {
      	foo: 'bar'
   		})
    }, 1000);
  }
});

templates.application.hbs

{{my-component}}

templates.components.my-component.hbs

<h1>Welcome to {{bar}}</h1>
<p>Check out the console to see how often computed properties are being re-computed and how often the component is being re-rendered</p>

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.4.2"
  }
}