Symfony2 Doctrine 事件监听器 prePersist 不起作用

Question

我在实现 Doctrine EventListener 时遇到问题。创建新发票时，InvoiceType 表单中包含一组项目(标题、价格、金额)。对于发票，在 price 字段中，我想插入所有购买产品的总和。在 ReportListener 中，我得到了总和，但 EventListener 没有预先保留数据，代码只是停止而不显示错误(程序在 ReportListener 中执行 $entityManager->persist($entity) 时停止)
这是一些代码
Controller

class InvoiceController extends Controller
{
    public function createAction(Request $request)
    {
        $em = $this->getDoctrine()->getManager();
        $company = $em->getRepository('DemoBundle:Company')
                      ->findOneByUser($this->getUser()->getId());
        $invoice = new Invoice();
        $item = new Item();
        $form = $this->createForm(new InvoiceType($company->getId()), $invoice);

        if($request->isMethod('POST')){
            if($form->isValid()){
                $em->persist($invoice);
                $em->flush();
            }
        }
    }
}

ReportListener

namespace Demo\Bundle\EventListener;

use Doctrine\ORM\Event\LifecycleEventArgs;
use Demo\Bundle\Entity\Invoice;

class ReportListener
{
    public function prePersist(LifecycleEventArgs $args)
    {
        $entity = $args->getEntity();
        $em = $args->getEntityManager();

        $priceTotal = 0;
        foreach ($entity->getItems() as $item)
        {
            $price = &$priceTotal;
            $price += $item->getPrice() * $item->getAmount();
        }

        $entity->setPriceTotal($priceTotal);       // this works
        $em->persist($entity);                     // here code stops
        $em->flush();
    }
}

service.yml

report.listener:
    class: Faktura\FakturaBundle\EventListener\ReportListener
    tags:
        - { name: doctrine.event_listener, event: prePersist }

Answer 1

prePersist 是一个被触发的事件，您不必也不应该尝试在该事件中自己持久化和刷新，Doctrine 会在它准备好时到达那里。基本上，只需删除最后几行:

$em->persist($entity);                     // here code stops
$em->flush();