.. versionadded:: 2.4
The Expression constraint was introduced in Symfony 2.4.
This constraint allows you to use an :ref:`expression <component-expression-language-examples>` for more complex, dynamic validation. See Basic Usage for an example. See :doc:`/reference/constraints/Callback` for a different constraint that gives you similar flexibility.
Imagine you have a class BlogPost with category and isTechnicalPost
properties:
namespace Acme\DemoBundle\Model;
use Symfony\Component\Validator\Constraints as Assert;
class BlogPost
{
private $category;
private $isTechnicalPost;
// ...
public function getCategory()
{
return $this->category;
}
public function setIsTechnicalPost($isTechnicalPost)
{
$this->isTechnicalPost = $isTechnicalPost;
}
// ...
}
To validate the object, you have some special requirements:
- If
isTechnicalPostis true, thencategorymust be eitherphporsymfony; - If
isTechnicalPostis false, thencategorycan be anything.
One way to accomplish this is with the Expression constraint:
.. configuration-block::
.. code-block:: yaml
# src/Acme/DemoBundle/Resources/config/validation.yml
Acme\DemoBundle\Model\BlogPost:
constraints:
- Expression:
expression: "this.getCategory() in ['php', 'symfony'] or !this.isTechnicalPost()"
message: "If this is a tech post, the category should be either php or symfony!"
.. code-block:: php-annotations
// src/Acme/DemoBundle/Model/BlogPost.php
namespace Acme\DemoBundle\Model;
use Symfony\Component\Validator\Constraints as Assert;
/**
* @Assert\Expression(
* "this.getCategory() in ['php', 'symfony'] or !this.isTechnicalPost()",
* message="If this is a tech post, the category should be either php or symfony!"
* )
*/
class BlogPost
{
// ...
}
.. code-block:: xml
<!-- src/Acme/DemoBundle/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\DemoBundle\Model\BlogPost">
<constraint name="Expression">
<option name="expression">
this.getCategory() in ['php', 'symfony'] or !this.isTechnicalPost()
</option>
<option name="message">
If this is a tech post, the category should be either php or symfony!
</option>
</constraint>
</class>
</constraint-mapping>
.. code-block:: php
// src/Acme/DemoBundle/Model/BlogPost.php
namespace Acme\DemoBundle\Model;
use Symfony\Component\Validator\Mapping\ClassMetadata;
use Symfony\Component\Validator\Constraints as Assert;
class BlogPost
{
public static function loadValidatorMetadata(ClassMetadata $metadata)
{
$metadata->addConstraint(new Assert\Expression(array(
'expression' => 'this.getCategory() in ["php", "symfony"] or !this.isTechnicalPost()',
'message' => 'If this is a tech post, the category should be either php or symfony!',
)));
}
// ...
}
The :ref:`expression <reference-constraint-expression-option>` option is the expression that must return true in order for validation to pass. To learn more about the expression language syntax, see :doc:`/components/expression_language/syntax`.
Mapping the Error to a Specific Field
You can also attach the constraint to a specific property and still validate
based on the values of the entire entity. This is handy if you want to attach
the error to a specific field. In this context, value represents the value
of isTechnicalPost.
.. configuration-block::
.. code-block:: yaml
# src/Acme/DemoBundle/Resources/config/validation.yml
Acme\DemoBundle\Model\BlogPost:
properties:
isTechnicalPost:
- Expression:
expression: "this.getCategory() in ['php', 'symfony'] or value == false"
message: "If this is a tech post, the category should be either php or symfony!"
.. code-block:: php-annotations
// src/Acme/DemoBundle/Model/BlogPost.php
namespace Acme\DemoBundle\Model;
use Symfony\Component\Validator\Constraints as Assert;
class BlogPost
{
// ...
/**
* @Assert\Expression(
* "this.getCategory() in ['php', 'symfony'] or value == false",
* message="If this is a tech post, the category should be either php or symfony!"
* )
*/
private $isTechnicalPost;
// ...
}
.. code-block:: xml
<!-- src/Acme/DemoBundle/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\DemoBundle\Model\BlogPost">
<property name="isTechnicalPost">
<constraint name="Expression">
<option name="expression">
this.getCategory() in ['php', 'symfony'] or value == false
</option>
<option name="message">
If this is a tech post, the category should be either php or symfony!
</option>
</constraint>
</property>
</class>
</constraint-mapping>
.. code-block:: php
// src/Acme/DemoBundle/Model/BlogPost.php
namespace Acme\DemoBundle\Model;
use Symfony\Component\Validator\Constraints as Assert;
use Symfony\Component\Validator\Mapping\ClassMetadata;
class BlogPost
{
public static function loadValidatorMetadata(ClassMetadata $metadata)
{
$metadata->addPropertyConstraint('isTechnicalPost', new Assert\Expression(array(
'expression' => 'this.getCategory() in ["php", "symfony"] or value == false',
'message' => 'If this is a tech post, the category should be either php or symfony!',
)));
}
// ...
}
.. versionadded:: 2.6
In Symfony 2.6, the Expression constraint *is* executed if the value
is ``null``. Before 2.6, if the value was ``null``, the expression
was never executed and the value was considered valid (unless you
also had a constraint like ``NotBlank`` on the property).
For more information about the expression and what variables are available to you, see the :ref:`expression <reference-constraint-expression-option>` option details below.
type: string [:ref:`default option <validation-default-option>`]
The expression that will be evaluated. If the expression evaluates to a false
value (using ==, not ===), validation will fail.
To learn more about the expression language syntax, see :doc:`/components/expression_language/syntax`.
Inside of the expression, you have access to up to 2 variables:
Depending on how you use the constraint, you have access to 1 or 2 variables in your expression:
this: The object being validated (e.g. an instance of BlogPost);value: The value of the property being validated (only available when the constraint is applied directly to a property);
type: string default: This value is not valid.
The default message supplied when the expression evaluates to false.