Define Property

controllers.application.js

import Ember from 'ember';
import { defineProperty } from '@ember/object';

export default Ember.Controller.extend({
  init() {
    setTimeout(() => {
      // This line works and is deprecated
      this.set('delayedProperty', Ember.computed(() => 'foo'));
      
      // Using defineProperty() does not trigger any computed properties that are watching the property (eg. textToShow)
      // defineProperty(this, 'delayedProperty', Ember.computed(() => 'foo'));
      
      // Just logging value for proof that delayedProperty does contain the correct value when set via defineProperty
      console.log('Delayed Property Value is:', this.delayedProperty);
    }, 2000);
  },
  delayedProperty: 'bar',
  textToShow: Ember.computed('delayedProperty', function() {
    return this.get('delayedProperty');
  })  
});

templates.application.hbs

<h1>Should change from bar to foo after 2sec ->{{textToShow}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>

twiddle.json

{
  "version": "0.15.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.2.2",
    "ember-template-compiler": "3.2.2",
    "ember-testing": "3.2.2"
  },
  "addons": {
    "ember-data": "3.2.0"
  }
}