lazy observer - Making observer to trigger only once using Ember.run.once

controllers.application.js

import Ember from 'ember';

let onceObserver = function(observerFunc, ...keys) {
  return Ember.observer(...keys, function() {
    Ember.run.once(this, observerFunc);
  });
}

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',

  myObserver: onceObserver(function() {
    alert('myObserver fired');
  }, 'foo', 'bar'),
  
  eagerObserver: Ember.observer('foo', 'bar', function() {
    alert('eagerObserver fired');
  }),

  actions: {
    setStuff() {
      this.set('foo', Math.random());
      this.set('bar', Math.random());
    }
  }
});

templates.application.hbs

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

<button {{action 'setStuff'}}>Set stuff</button>

twiddle.json

{
  "version": "0.10.5",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.8.0",
    "ember-data": "2.8.0",
    "ember-template-compiler": "2.8.0",
    "ember-testing": "2.8.0"
  },
  "addons": {}
}