"Page not found" on custom module

Question

I did a custom module, but i can't see the page with the URL : Page not found. I can install the module and activiate, but i can't go on the page.

This is the code :

hello_world.hello_world:
  path: '/helloworld'
  defaults:
    _controller: 'Drupal\hello_world\Controller\HelloWorldController::helloWorld'
    _title: 'Hello World'
  requirements:
    _permission: 'access content'

---

name: Hello World
core: 8.x
type: module
package: Tutos
description: Mini module test Drupal 8

---

<?php
/**
 * @file
* Contains \Drupal\hello_world\Controller\HelloWorldController.
*/

namespace Drupal\hello_world\Controller;
use Drupal\Core\Controller\ControllerBase;

/**
 * Controller routines for hello_world module routes.
 */
class HelloWorldController extends ControllerBase {

  /**
   * Return the 'Hello World' page.
   *
   * @return string
   *   A render array containing our 'Hello World' page content.
   */
  public function helloWorld() {
    $output = array();

    $output['hello_world'] = array(
        '#markup' => $this->t('Hello World!'),
    );
    return $output;
  }
}

Answer 1

You may need a leading \ for the controller definition.