QP Service

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  paramsService: Ember.inject.service('params'),
  appName: 'Ember Twiddle',
  queryParams: ['theme'],
  theme: 'bye',
  counter: 0,
  
  init() {
     this._super(...arguments);
    var paramsService = this.get('paramsService');
    
    paramsService.subscribe('theme', theme => this.set('theme', theme));
  },
  
  actions: {
  	updateTheme() {
    	var paramsService = this.get('paramsService');
      var counter = this.incrementProperty('counter');
      
      paramsService.setParam('theme', `hi${counter}`);
    }
  }
});

services.params.js

import Ember from 'ember';

const map = new Map();

export default Ember.Service.extend({
  setParam(name, val) {
    this.set(name, val);

    if (map.has(name)) {
      let cb = map.get(name);
      cb(val);
    }
  },

  subscribe(name, cb) {
    map.set(name, cb);
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>
<button type="button" {{action 'updateTheme'}}>Test</button><br>
{{theme}}

twiddle.json

{
  "version": "0.7.2",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.4.4",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.4.3/ember-data.js",
    "ember-template-compiler": "2.4.4"
  }
}