Example controller

blog-posts.js

import Ember from 'ember';
// in Ember 3.x, you would use import Controller from '@ember/controller';

export default Ember.Controller.extend({
// in Ember 3.x, use export default Controller.extend({
  
  blogPostTopic: '',
  queryParams: [{
    blogPostTopic: {
      type: 'string',
      refreshModel: true
      // refreshModel says whether the model hook on the route should be re-run if the query parameter changes. Its default is false!
    }
  }], 
  actions: {
    changeQueryParam(topic) {
    	this.set('blogPostTopic', topic)
    }
  }
});