symfony2 达到最大函数嵌套级别 '100'，中止!与学说事件监听器

Question

我有事件监听器 preUpdate

public function preUpdate(PreUpdateEventArgs $args) {        
    $user = $args->getEntity();
    if($user instanceof \iTracker\UserBundle\Entity\User) {
        if($args->hasChangedField('userGroup')) {

            $old = $args->getOldValue('userGroup');
            $new = $args->getNewValue('userGroup');

            $em = $args->getEntityManager();

            $old->setAmount($old->getAmount() - 1);
            $em->persist($old);

            $new->setAmount($new->getAmount() + 1);
            $em->persist($new);
            $em->flush();
        }
    }
}

提交表单后，我得到 FatalErrorException: Error: Maximum function nesting level of '100' reached, aborting!在/var/www/issue/app/cache/dev/classes.php 第 6123 行

in /var/www/issue/app/cache/dev/classes.php line 6123 at ErrorHandler->handleFatal() in /var/www/issue/vendor/symfony/symfony/src/Symfony/Component/HttpKernel/Debug/ErrorHandler.php line 0 at NormalizerFormatter->normalize() in /var/www/issue/app/cache/dev/classes.php line 6198 at LineFormatter->normalize() in /var/www/issue/app/cache/dev/classes.php line 6112 at NormalizerFormatter->format() in /var/www/issue/app/cache/dev/classes.php line 6172 at LineFormatter->format() in /var/www/issue/app/cache/dev/classes.php line 6320 at AbstractProcessingHandler->handle() in /var/www/issue/app/cache/dev/classes.php line 6646 at Logger->addRecord() in /var/www/issue/app/cache/dev/classes.php line 6710 at Logger->debug() in /var/www/issue/vendor/symfony/symfony/src/Symfony/Bridge/Doctrine/Logger/DbalLogger.php line 72 at DbalLogger->log() in /var/www/issue/vendor/symfony/symfony/src/Symfony/Bridge/Doctrine/Logger/DbalLogger.php line 50 at DbalLogger->startQuery() in /var/www/issue/vendor/doctrine/dbal/lib/Doctrine/DBAL/Logging/LoggerChain.php line 50 at LoggerChain->startQuery() in /var/www/issue/vendor/doctrine/dbal/lib/Doctrine/DBAL/Connection.php line 774 at Connection->executeUpdate() in /var/www/issue/vendor/doctrine/orm/lib/Doctrine/ORM/Persisters/BasicEntityPersister.php line 447 at BasicEntityPersister->_updateTable() in /var/www/issue/vendor/doctrine/orm/lib/Doctrine/ORM/Persisters/BasicEntityPersister.php line 357 at BasicEntityPersister->update() in /var/www/issue/vendor/doctrine/orm/lib/Doctrine/ORM/UnitOfWork.php line 984 at UnitOfWork->executeUpdates() in /var/www/issue/vendor/doctrine/orm/lib/Doctrine/ORM/UnitOfWork.php line 317 at UnitOfWork->commit() in /var/www/issue/vendor/doctrine/orm/lib/Doctrine/ORM/EntityManager.php line 355 at EntityManager->flush() in /var/www/issue/src/iTracker/UserBundle/Listener/UserGroupAmount.php line 41 and this

• 在 UserGroupAmount->preUpdate() 中/var/www/issue/vendor/symfony/symfony/src/Symfony/Bridge/Doctrine/ContainerAwareEventManager.php第61行
• 在 ContainerAwareEventManager->dispatchEvent() 中/var/www/issue/vendor/doctrine/orm/lib/Doctrine/ORM/UnitOfWork.php980行
• 在 UnitOfWork->executeUpdates() 中/var/www/issue/vendor/doctrine/orm/lib/Doctrine/ORM/UnitOfWork.php第317行
• 在 UnitOfWork->commit() 中/var/www/issue/vendor/doctrine/orm/lib/Doctrine/ORM/EntityManager.php第355行
• 在 EntityManager->flush() 中/var/www/issue/src/iTracker/UserBundle/Listener/UserGroupAmount.php第 41 行

并且循环了这5个错误，导致了这个异常

Answer 1

@meze 是对的，在 *Flush* 事件中使用 flush 会导致循环。

但是有一个快速的解决方法可以让您仍然这样做: $eventManager = $this -> em -> getEventManager();

// Remove event, if we call $this->em->flush() now there is no infinite recursion loop!
$eventManager -> removeEventListener('onFlush', $this); 

// ...

// Re-attach since we're done
$eventManager -> addEventListener('onFlush', $this); 

出现在:Doctrine2 Event Listener: persisting in onFlush() | Benedikt Wolters