Eccube\Service\CartService::setPreOrderId PHP Method

    public function setPreOrderId($pre_order_id)
    {
        $this->cart->setPreOrderId($pre_order_id);
        return $this;
    }

 /**
  * 受注情報を作成
  *
  * @param $Customer
  * @return \Eccube\Entity\Order
  */
 public function createOrder($Customer)
 {
     // ランダムなpre_order_idを作成
     $preOrderId = sha1(Str::random(32));
     // 受注情報、受注明細情報、お届け先情報、配送商品情報を作成
     $Order = $this->registerPreOrder($Customer, $preOrderId);
     $this->cartService->setPreOrderId($preOrderId);
     $this->cartService->save();
     return $Order;
 }