Partial references with Doctrine

partial_refs.php

<?php

     
protected function getCart($clientCode, $salesmanCode)                                     
{                                                                                          
    $em = $this->getDoctrine()->getEntityManager();                                        
                                                                                                 
          $cart = $em->getRepository('TheodoExtranetBundle:ShoppingCart')                      
            ->findOneBy(array(                                                                 
                  'customerCode' => $clientCode,                                                 
                  'salesmanCode' => $salesmanCode,                                               
                  'status'       => \Theodo\ExtranetBundle\Entity\ShoppingCart::STATUS_OPEN,              ));                                                                                
                                                                                                 
          if (!$cart instanceof ShoppingCart) {                                                  
              $cart = new ShoppingCart();                                                        
              $cart->setCustomer(                                                                
                  $em->getPartialReference(                                                      
                      'Theodo\ShopDataBundle\Entity\Customer',                                 
                      $clientCode                                                                
                  ));                                                                            
              $cart->setSalesman(                                                                
                  $em->getPartialReference(                                                      
                      'Theodo\ShopDataBundle\Entity\Customer',                                 
                      $salesmanCode                                                              
                ));                                                                            
              $cart->setBrand('00');                                                             
              $cart->setBrandName('extranet');                                                   
              $em->merge($cart);                                                                 
              $em->flush();                                                                      
    }                                                                                      
                                                                                                 
    return $cart;                                                                          
}