Validates that a value is blank - meaning equal to an empty string or null:
if ('' !== $value && null !== $value) {
// validation will fail
}
To force that a value strictly be equal to null, see the
:doc:`/reference/constraints/IsNull` constraint.
To force that a value is not blank, see :doc:`/reference/constraints/NotBlank`.
But be careful as NotBlank is not strictly the opposite of Blank.
If, for some reason, you wanted to ensure that the firstName property
of an Author class were blank, you could do the following:
.. configuration-block::
.. code-block:: php-annotations
// src/AppBundle/Entity/Author.php
namespace AppBundle\Entity;
use Symfony\Component\Validator\Constraints as Assert;
class Author
{
/**
* @Assert\Blank()
*/
protected $firstName;
}
.. code-block:: yaml
# src/AppBundle/Resources/config/validation.yml
AppBundle\Entity\Author:
properties:
firstName:
- Blank: ~
.. code-block:: xml
<!-- src/AppBundle/Resources/config/validation.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<constraint-mapping xmlns="http://symfony.com/schema/dic/constraint-mapping"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://symfony.com/schema/dic/constraint-mapping http://symfony.com/schema/dic/constraint-mapping/constraint-mapping-1.0.xsd">
<class name="AppBundle\Entity\Author">
<property name="firstName">
<constraint name="Blank" />
</property>
</class>
</constraint-mapping>
.. code-block:: php
// src/AppBundle/Entity/Author.php
namespace AppBundle\Entity;
use Symfony\Component\Validator\Mapping\ClassMetadata;
use Symfony\Component\Validator\Constraints as Assert;
class Author
{
public static function loadValidatorMetadata(ClassMetadata $metadata)
{
$metadata->addPropertyConstraint('firstName', new Assert\Blank());
}
}
type: string default: This value should be blank.
This is the message that will be shown if the value is not blank.