当未找到结果时，HYDRATE_SINGLE_SCALAR将导致getOneOrNullResult中的异常

Question

当我尝试使用以Doctrine\ORM\Query#getOneOrNullResult为水合模式的HYDRATE_SINGLE_SCALAR方法时，如果没有找到结果，就会抛出Doctrine\ORM\NoResultException：

$q=$em->createQueryBuilder()
    ->select('ticket.tickets_id')
    ->from('e:Ticket','ticket')
    ->where('ticket.ticketnumber=:ticketnumber')
    ->setParameter('ticketnumber','kr1r9x')
    ->getQuery()
;
// these both work:
var_dump($q->getOneOrNullResult(Query::HYDRATE_SCALAR));
var_dump($q->getOneOrNullResult(Query::HYDRATE_SINGLE_SCALAR));

$q=$em->createQueryBuilder()
    ->select('ticket.tickets_id')
    ->from('e:Ticket','ticket')
    ->where('ticket.ticketnumber=:ticketnumber')
    ->setParameter('ticketnumber','foobar')
    ->getQuery()
;
// this works
var_dump($q->getOneOrNullResult(Query::HYDRATE_SCALAR));
// this fails
var_dump($q->getOneOrNullResult(Query::HYDRATE_SINGLE_SCALAR));

我希望在最后一次调用中返回NULL，但实际输出是：

% php ~/test.php
array(1) {
  'tickets_id' =>
  string(6) "119827"
}
string(6) "119827"
NULL
Fatal error: Uncaught exception 'Doctrine\ORM\NoResultException' with message 'No result was found for query although at least one row was expected.' in ~/project/vendor/doctrine/orm/lib/Doctrine/ORM/Internal/Hydration/SingleScalarHydrator.php on line 43

Doctrine\ORM\NoResultException: No result was found for query although at least one row was expected. in ~/project/vendor/doctrine/orm/lib/Doctrine/ORM/Internal/Hydration/SingleScalarHydrator.php on line 43

Call Stack:
    0.0002     640440   1. {main}() ~/test.php:0
    0.1575   15011776   2. Doctrine\ORM\AbstractQuery->getOneOrNullResult() ~/test.php:28
    0.1575   15011824   3. Doctrine\ORM\AbstractQuery->execute() ~/project/vendor/doctrine/orm/lib/Doctrine/ORM/AbstractQuery.php:612
    0.1581   15016432   4. Doctrine\ORM\Internal\Hydration\AbstractHydrator->hydrateAll() ~/project/vendor/doctrine/orm/lib/Doctrine/ORM/AbstractQuery.php:804
    0.1581   15016432   5. Doctrine\ORM\Internal\Hydration\SingleScalarHydrator->hydrateAllData() ~/project/vendor/doctrine/orm/lib/Doctrine/ORM/Internal/Hydration/AbstractHydrator.php:140

难道不可能以这种方式获得单个标量或NULL吗？

(我知道解决办法是使用HYDRATE_SCALAR，我只是想知道为什么HYDRATE_SINGLE_SCALAR不能工作)

原则ORM v2.4.5，DBAL &CommonV2.4.2

Answer 1

NULL不是标量值，所以在找不到行时，原则抛出异常是正确的。

正确的处理方法是捕获和处理异常。您可以选择将结果设置为NULL，执行另一个操作，或通过抛出自己的异常来抽象异常。例如，如果您试图为结果设置一个变量：

// After defining QueryBuilder $q
try {
    $result = $q->getOneOrNullResult(Query::HYDRATE_SINGLE_SCALAR);
} catch (\Doctrine\ORM\NoResultException $e) {
    // Handle the exception here. In this case, we are setting the variable to NULL
    $result = null;
}

至于HYDRATE_SCALAR和HYDRATE_SINGLE_SCALAR: HYDRATE_SINGLE_SCALAR之间的区别，它只返回一个值，因此如果它没有要返回的值，则必须抛出一个错误。HYDRATE_SCALAR返回任意数量的值的数组，包括0，所以它可以返回0结果。