Tuto Créer un router, j'ai un message d'erreur

Bonjour,

a la minute 39 et 46 seconds a ce tutoriel https://www.youtube.com/watch?v=I-DN2C7Gs7A

j'ai un message d'erreur

Fatal error: Uncaught exception 'App\Router\RouterException' with message 'No route matches this name' in C:\xampp\htdocs\Grafikart\src\Router\Router.php:48 Stack trace: #0 C:\xampp\htdocs\Grafikart\index.php(13): App\Router\Router->url('posts.show', Array) #1 [internal function]: {closure}('48', 'salut-les-gens') #2 C:\xampp\htdocs\Grafikart\src\Router\Route.php(47): call_user_func_array(Object(Closure), Array) #3 C:\xampp\htdocs\Grafikart\src\Router\Router.php(39): App\Router\Route->call() #4 C:\xampp\htdocs\Grafikart\index.php(27): App\Router\Router->run() #5 {main} thrown in C:\xampp\htdocs\Grafikart\src\Router\Router.php on line 48

j'utilise l'autoloader.php parce que je ne comprend pas au debut de tuto le composer

et voila mon code

Autoloader.php

<?php 
namespace App;

class Autoloader{

static function register(){
   spl_autoload_register(array(__CLASS__, 'autoload'));
}

static function autoload($class){     
  if(strpos($class, __NAMESPACE__.'\\') === 0){
     $class = str_replace(__NAMESPACE__, '', $class);
     $class = str_replace('\\', '/', $class);    
     require 'src/'.$class.'.php';
   }
}

}

?>

index.php

<?php
use \App\Autoloader; 
require 'vendor/Autoloader.php';
Autoloader::register();

$router = new App\Router\Router($_GET['url']);

$router->get('/', function(){ echo "homepage"; });
$router->get('/posts', function(){ echo 'Tous les articles'; });

$router->get('/posts/:id-:slug', function($id, $slug) use ($router) { echo $router->url('posts.show', ['id' => 1, 'slug' => 'salut-les-gens']); }, 'posts-show')->with('id', '[0-9]+')->with('slug', '([a-z\-0-9]+)');

$router->get('/posts/:id', function($id){
?>
<form action="" method="post">
   <input type="text" name="name">
   <button type="submit">Envoyer</button>
</form>
<?php

 });
$router->post('/posts/:id', function($id){ echo 'Poster pour l\'article '.$id.'<pre>'.print_r($_POST, true).'</pre>'; });

$router->run();

?>

Router.php

<?php 
namespace App\Router;

class Router{

   private $url;
   private $routes = [];
   private $namedRoutes = [];

   public function __construct($url){
     $this->url = $url;
   }

   public function get($path, $callable, $name = null){
     return $this->add($path, $callable, $name, 'GET');
   }

   public function post($path, $callable, $name = null){
      return $this->add($path, $callable, $name, 'POST');
   }

   private function add($path, $callable, $name, $method){
      $route = new Route($path, $callable);
      $this->routes[$method][] = $route;
      if($name){
         $this->namedRoutes[$name] = $route;
      }
      return $route;
   }

   public function run(){
     if(!isset($this->routes[$_SERVER['REQUEST_METHOD']])){
        throw new RouterException('REQUEST_METHOD does not exist');
     }

     foreach($this->routes[$_SERVER['REQUEST_METHOD']] as $route){
       if($route->match($this->url)){
          return $route->call();
       }
     }
     var_dump($this->matches);
     throw new RouterException('No matching routes');
   }

   public function url($name, $params = []){
        if(!isset($this->namedRoutes[$name])){
            throw new RouterException('No route matches this name');
        }
        return $this->namedRoutes[$name]->getUrl($params);
    }

}

?>

RouterException.php

namespace App\Router;

class RouterException extends \Exception {

}

Route.php

<?php 
namespace App\Router;

class Route {

   private $path;
   private $callable;
   private $matches;
   private $params = [];

   public function __construct($path, $callable){

      $this->path = trim($path, '/');
      $this->callable = $callable;

   }

   public function with($param, $regex){
     $this->params[$param] = str_replace('(', '(?:', $regex);
     return $this;
   }

   public function match($url){
     $url = trim($url, '/');
    // print_r($this->path);
     $path = preg_replace_callback('#:([\w]+)#', [$this, 'paramMatch'], $this->path);
     $regex = "#^$path$#i";  

     if(!preg_match($regex, $url, $matches)){
         return false;
     }
     array_shift($matches);
     $this->matches = $matches;
     return true;
   }

   private function paramMatch($match){
     if(isset($this->params[$match[1]])){
         return '('.$this->params[$match[1]].')';
     }
      return '([^/]+)';

   } 

   public function call(){     
      return call_user_func_array($this->callable, $this->matches);
   }

   public function getUrl($params){
      $path = $this->path;
      foreach($params as $k => $v){
         $path = str_replace(":$k", $v, $path);
      }
      return $path;
   }
}

?>