https://stackoverflow.com/questions/45505060/ember-ajax-idicator-in-model

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  queryParams:['search'],
  actions:{
    onSearch(value){
      //this is where it will start transitioning. it will call model hook.
      this.set('search',value);
    }
  }
});

routes.application.js

import Ember from 'ember';

export default Ember.Route.extend({
  queryParams:{ search: { refreshModel: true} },
  model(params){
    console.log(' paramss ',params.search);
    return new Ember.RSVP.Promise((resolve)=>{
      Ember.run.later(()=> {
        resolve(params.search);
      }, 3000);
    });
  },
  actions:{
    loading(transition, originRoute) {
            //if you want to set controller property, this.controller.set('isLoading',true); will do
            this.controller.set('isLoading',true);
            console.log(' loading state starts');
            transition.promise.finally(()=> {
               this.controller.set('isLoading',false);   
              console.log(' loading ends');
            });
      return true;
        }    
  }
});

templates.application-loading.hbs

Loading from loading.hbs...

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
{{#if isLoading}}
Loading..
{{/if}}
<br>
{{model}}
<br>
<input type="text" value={{search}} oninput={{action 'onSearch' value='target.value'}} /> 
{{outlet}}
<br>
<br>

twiddle.json

{
  "version": "0.11.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.11.0",
    "ember-data": "2.11.0",
    "ember-template-compiler": "2.11.0",
    "ember-testing": "2.11.0"
  },
  "addons": {}
}