child queryParam

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

controllers.parent.child.js

import Ember from 'ember';
import { inject as controller } from '@ember/controller';

export default Ember.Controller.extend({
  parentController: controller('parent'),
  foo: Ember.computed.alias('parentController.foo')
});

router.js

import EmberRouter from '@ember/routing/router';
import config from './config/environment';

const Router = EmberRouter.extend({
  location: 'none',
  rootURL: config.rootURL
});

Router.map(function() {
  this.route('parent', function() {
  	this.route('child');
  })
});

export default Router;

routes.parent.js

import Ember from 'ember';

export default Ember.Route.extend({
  queryParams: {
    foo: {}
  }
});

templates.application.hbs

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

templates.index.hbs

{{link-to 'foo' 'parent.child' (query-params foo='foo')}}

templates.parent.child.hbs

<h3>child</h3>
queryParam is {{foo}}

<br/>

{{link-to 'a' 'parent.child' (query-params foo='a')}}
{{link-to 'b' 'parent.child' (query-params foo='b')}}
{{link-to 'c' 'parent.child' (query-params foo='c')}}

templates.parent.hbs

<h3>Parent</h3>
queryParam is {{foo}}
{{outlet}}

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"
  }
}