.. index:: single: Validation; Custom constraints
You can create a custom constraint by extending the base constraint class, :class:`Symfony\\Component\\Validator\\Constraint`. As an example you're going to create a simple validator that checks if a string contains only alphanumeric characters.
First you need to create a Constraint class and extend :class:`Symfony\\Component\\Validator\\Constraint`:
// src/Acme/DemoBundle/Validator/Constraints/ContainsAlphanumeric.php
namespace Acme\DemoBundle\Validator\Constraints;
use Symfony\Component\Validator\Constraint;
/**
* @Annotation
*/
class ContainsAlphanumeric extends Constraint
{
public $message = 'The string "%string%" contains an illegal character: it can only contain letters or numbers.';
}
Note
The @Annotation annotation is necessary for this new constraint in
order to make it available for use in classes via annotations.
Options for your constraint are represented as public properties on the
constraint class.
As you can see, a constraint class is fairly minimal. The actual validation is
performed by another "constraint validator" class. The constraint validator
class is specified by the constraint's validatedBy() method, which
includes some simple default logic:
// in the base Symfony\Component\Validator\Constraint class
public function validatedBy()
{
return get_class($this).'Validator';
}
In other words, if you create a custom Constraint (e.g. MyConstraint),
Symfony2 will automatically look for another class, MyConstraintValidator
when actually performing the validation.
The validator class is also simple, and only has one required method validate():
// src/Acme/DemoBundle/Validator/Constraints/ContainsAlphanumericValidator.php
namespace Acme\DemoBundle\Validator\Constraints;
use Symfony\Component\Validator\Constraint;
use Symfony\Component\Validator\ConstraintValidator;
class ContainsAlphanumericValidator extends ConstraintValidator
{
public function validate($value, Constraint $constraint)
{
if (!preg_match('/^[a-zA-Za0-9]+$/', $value, $matches)) {
$this->context->addViolation($constraint->message, array('%string%' => $value));
}
}
}
Note
The validate method does not return a value; instead, it adds violations
to the validator's context property with an addViolation method
call if there are validation failures. Therefore, a value could be considered
as being valid if it causes no violations to be added to the context.
The first parameter of the addViolation call is the error message to
use for that violation.
Using custom validators is very easy, just as the ones provided by Symfony2 itself:
.. configuration-block::
.. code-block:: yaml
# src/Acme/BlogBundle/Resources/config/validation.yml
Acme\DemoBundle\Entity\AcmeEntity:
properties:
name:
- NotBlank: ~
- Acme\DemoBundle\Validator\Constraints\ContainsAlphanumeric: ~
.. code-block:: php-annotations
// src/Acme/DemoBundle/Entity/AcmeEntity.php
use Symfony\Component\Validator\Constraints as Assert;
use Acme\DemoBundle\Validator\Constraints as AcmeAssert;
class AcmeEntity
{
// ...
/**
* @Assert\NotBlank
* @AcmeAssert\ContainsAlphanumeric
*/
protected $name;
// ...
}
.. 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\Entity\AcmeEntity">
<property name="name">
<constraint name="NotBlank" />
<constraint name="Acme\DemoBundle\Validator\Constraints\ContainsAlphanumeric" />
</property>
</class>
</constraint-mapping>
.. code-block:: php
// src/Acme/DemoBundle/Entity/AcmeEntity.php
use Symfony\Component\Validator\Mapping\ClassMetadata;
use Symfony\Component\Validator\Constraints\NotBlank;
use Acme\DemoBundle\Validator\Constraints\ContainsAlphanumeric;
class AcmeEntity
{
public $name;
public static function loadValidatorMetadata(ClassMetadata $metadata)
{
$metadata->addPropertyConstraint('name', new NotBlank());
$metadata->addPropertyConstraint('name', new ContainsAlphanumeric());
}
}
If your constraint contains options, then they should be public properties on the custom Constraint class you created earlier. These options can be configured like options on core Symfony constraints.
If your constraint validator has dependencies, such as a database connection,
it will need to be configured as a service in the dependency injection
container. This service must include the validator.constraint_validator
tag and an alias attribute:
.. configuration-block::
.. code-block:: yaml
services:
validator.unique.your_validator_name:
class: Fully\Qualified\Validator\Class\Name
tags:
- { name: validator.constraint_validator, alias: alias_name }
.. code-block:: xml
<service id="validator.unique.your_validator_name" class="Fully\Qualified\Validator\Class\Name">
<argument type="service" id="doctrine.orm.default_entity_manager" />
<tag name="validator.constraint_validator" alias="alias_name" />
</service>
.. code-block:: php
$container
->register('validator.unique.your_validator_name', 'Fully\Qualified\Validator\Class\Name')
->addTag('validator.constraint_validator', array('alias' => 'alias_name'));
Your constraint class should now use this alias to reference the appropriate validator:
public function validatedBy()
{
return 'alias_name';
}
As mentioned above, Symfony2 will automatically look for a class named after
the constraint, with Validator appended. If your constraint validator
is defined as a service, it's important that you override the
validatedBy() method to return the alias used when defining your service,
otherwise Symfony2 won't use the constraint validator service, and will
instantiate the class instead, without any dependencies injected.
Beside validating a class property, a constraint can have a class scope by
providing a target in its Constraint class:
public function getTargets()
{
return self::CLASS_CONSTRAINT;
}
With this, the validator validate() method gets an object as its first argument:
class ProtocolClassValidator extends ConstraintValidator
{
public function validate($protocol, Constraint $constraint)
{
if ($protocol->getFoo() != $protocol->getBar()) {
$this->context->addViolationAt('foo', $constraint->message, array(), null);
}
}
}
Note that a class constraint validator is applied to the class itself, and not to the property:
.. configuration-block::
.. code-block:: yaml
# src/Acme/BlogBundle/Resources/config/validation.yml
Acme\DemoBundle\Entity\AcmeEntity:
constraints:
- Acme\DemoBundle\Validator\Constraints\ContainsAlphanumeric: ~
.. code-block:: php-annotations
/**
* @AcmeAssert\ContainsAlphanumeric
*/
class AcmeEntity
{
// ...
}
.. code-block:: xml
<!-- src/Acme/BlogBundle/Resources/config/validation.xml -->
<class name="Acme\DemoBundle\Entity\AcmeEntity">
<constraint name="Acme\DemoBundle\Validator\Constraints\ContainsAlphanumeric" />
</class>