Serialize objects in QP

controllers.application.js

import Controller from '@ember/controller';
import { reads } from '@ember/object/computed';

export default Controller.extend({
  queryParams: ['theObject'],
  
  actions: {
    updateTheObject() {
      this.set('theObject', { appName: this.appName });
    }
  }
});

routes.application.js

import Route from '@ember/routing/route';

export default Route.extend({
  queryParams: {
    theObject: { type: 'object' }
  },
  
  setupController(controller) {
    this._super(...arguments);
    controller.set('appName', 'Test');
  },
  
  serializeQueryParam(value, key, type) {
    if (type !== 'object') return this._super(...arguments);
    return JSON.stringify(value);
  },
  
  deserializeQueryParam(value, key, type) {
    if (type !== 'object') return this._super(...arguments);
    return JSON.parse(value);
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{input value=this.appName enter=(action "updateTheObject")}}
<br>
<br>

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.4.2"
  }
}