CP-fire-twice

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  myService: Ember.inject.service(),
  appName: 'Ember Twiddle',
  
  init() {
    console.log('controller#init');
    this.get('myService').setProperties({a: 1, b: 2 });
  }
});

services.my-service.js

import Ember from 'ember';

const { computed } = Ember;

export default Ember.Service.extend({
  a: computed({
    set(_, v) {
      this.callMethod('a');
      return v;
    }
  }),
  
    b: computed({
    set(_, v) {
      this.callMethod('b');
      return v;
    }
  }),
  
  callMethod(str) {
     console.log('my-service#callmethod was called with ' + str);
  }
});

templates.application.hbs

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

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"
  }
}