Doctrine2 ORM不会保存对DateTime字段的更改

Question

我有一个用户实体:

use Doctrine\ORM\Mapping as ORM;

/**
 * ExampleBundle\Entity\User
 *
 * @ORM\Entity()
 */
class User
{
    // ...

    /**
     * @ORM\Column(type="service_expires_at", type="date", nullable=true)
     */
    private $service_expires_at;

    public function getServiceExpiresAt()
    {
        return $this->service_expires_at;
    }

    public function setServiceExpiresAt(\DateTime $service_expires_at)
    {
        $this->service_expires_at = $service_expires_at;
    }
}

当我将用户更新service_expires_at为以下内容时,更新后的service_expires_at值不会保存回数据库:

$date = $user->getServiceExpiresAt(); 

var_dump($date->format('Y-m-d')); // 2013-03-08

$date->modify('+10 days');

var_dump($date->format('Y-m-d')); // 2013-03-18

$user->setServiceExpiresAt($date);

$em->persist($user);
$em->flush();

但是,如果我传递一个新DateTime对象service_expires_at,则更新的值将正确保存:

$date = $user->getServiceExpiresAt(); 

$date->modify('+10 days');

$user->setServiceExpiresAt(new \DateTime($date->format('Y-m-d'));

$em->persist($user);
$em->flush();

为什么会这样？

Answer 1

DateTime返回的实例ExampleBundle\Entity\User#getServiceExpiresAt() 是存储在实体本身中的相同对象,这会破坏封装.

Doctrine ORM中的UnitOfWork对变更集应用严格比较,这基本上意味着在包含对象的实体的属性的情况下,如果对象实例未更改,则ORM不会检测到更改.

严格比较,以下是真实的:

$dateTime1 = new \DateTime('@0');
$dateTime2 = new \DateTime('@0');
$dateTime3 = $dateTime1;

var_dump($dateTime1 !== $dateTime2); // true
var_dump($dateTime1 === $dateTime3); // true

$dateTime1->modify('+1 day');

var_dump($dateTime1 === $dateTime3); // true

这是OOP编程中新手的一个常见错误,可以通过修复getter和setter来快速解决,以便原始实例永远不会在对象之外共享,如下例所示:

public function getServiceExpiresAt()
{
    return clone $this->service_expires_at;
}

public function setServiceExpiresAt(\DateTime $service_expires_at)
{
    $this->service_expires_at = clone $service_expires_at;
}

这也将解决Doctrine ORM的问题.

此外,请注意,这可以修复逻辑中可能存在的泄漏.例如,以下代码是错误的并且难以调试(当应用您当前损坏的getter/setter时):

$bankTransaction1 = $someService->getTransaction(1);
$bankTransaction2 = $someService->getTransaction(2);

// leak! Now both objects reference the same DateTime instance!
$bankTransaction2->setDateTime($bankTransaction1->getDateTime());

// bug! now both your objects were modified!
$bankTransaction1->getDateTime()->modify('+1 day');

因此,无论问题中的ORM部分如何,请不要破坏封装.