Null¶

Validates that a value is exactly equal to null. To force that a property is simply blank (blank string or null), see the Blank constraint. To ensure that a property is not null, see NotNull.

Applies to	property or method
Options	message
Class	`Null`
Validator	`NullValidator`

Basic Usage¶

If, for some reason, you wanted to ensure that the firstName property of an Author class exactly equal to null, you could do the following:

YAML

# src/Acme/BlogBundle/Resources/config/validation.yml
Acme\BlogBundle\Entity\Author:
    properties:
        firstName:
            - 'Null': ~

Annotations

// src/Acme/BlogBundle/Entity/Author.php
namespace Acme\BlogBundle\Entity;

use Symfony\Component\Validator\Constraints as Assert;

class Author
{
    /**
     * @Assert\Null()
     */
    protected $firstName;
}

XML

<!-- src/Acme/BlogBundle/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="Acme\BlogBundle\Entity\Author">
        <property name="firstName">
            <constraint name="Null" />
        </property>
    </class>
</constraint-mapping>

PHP

// src/Acme/BlogBundle/Entity/Author.php
namespace Acme\BlogBundle\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', Assert\Null());
    }
}

警告

When using YAML, be sure to surround Null with quotes ('Null') or else YAML will convert this into a null value.

Options¶

message¶

type: string default: This value should be null.

This is the message that will be shown if the value is not null.