UniqueEntity
============

Validates that a particular field (or fields) in a Doctrine entity is (are)
unique. This is commonly used, for example, to prevent a new user to register
using an email address that already exists in the system.

+----------------+-------------------------------------------------------------------------------------+
| Applies to     | :ref:`class<validation-class-target>`                                               |
+----------------+-------------------------------------------------------------------------------------+
| Options        | - `fields`_                                                                         |
|                | - `message`_                                                                        |
|                | - `em`_                                                                             |
+----------------+-------------------------------------------------------------------------------------+
| Class          | :class:`Symfony\\Bridge\\Doctrine\\Validator\\Constraints\\UniqueEntity`            |
+----------------+-------------------------------------------------------------------------------------+
| Validator      | :class:`Symfony\\Bridge\\Doctrine\\Validator\\Constraints\\UniqueEntityValidator`   |
+----------------+-------------------------------------------------------------------------------------+

Basic Usage
-----------

Suppose you have an ``AcmeUserBundle`` bundle with a ``User`` entity that has an
``email`` field. You can use the ``UniqueEntity`` constraint to guarantee that
the ``email`` field remains unique between all of the constraints in your user
table:

.. configuration-block::

    .. code-block:: php-annotations

        // Acme/UserBundle/Entity/User.php
        use Symfony\Component\Validator\Constraints as Assert;
        use Doctrine\ORM\Mapping as ORM;

        // DON'T forget this use statement!!!
        use Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity;

        /**
         * @ORM\Entity
         * @UniqueEntity("email")
         */
        class Author
        {
            /**
             * @var string $email
             *
             * @ORM\Column(name="email", type="string", length=255, unique=true)
             * @Assert\Email()
             */
            protected $email;
            
            // ...
        }

    .. code-block:: yaml

        # src/Acme/UserBundle/Resources/config/validation.yml
        Acme\UserBundle\Entity\Author:
            constraints:
                - Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity: email
            properties:
                email:
                    - Email: ~

    .. code-block:: xml

        <class name="Acme\UserBundle\Entity\Author">
            <constraint name="Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity">
                <option name="fields">email</option>
                <option name="message">This email already exists.</option>
            </constraint>
             <property name="email">
                <constraint name="Email" />
            </property>
        </class>

Options
-------

fields
~~~~~~

**type**: ``array``|``string`` [:ref:`default option<validation-default-option>`]

This required option is the field (or list of fields) on which this entity
should be unique. For example, if you specified both the ``email`` and ``name``
field in a single ``UniqueEntity`` constraint, then it would enforce that
the combination value where unique (e.g. two users could have the same email,
as long as they don't have the same name also).

If you need to require two fields to be individually unique (e.g. a unique
``email`` *and* a unique ``username``), you use two ``UniqueEntity`` entries,
each with a single field.

message
~~~~~~~

**type**: ``string`` **default**: ``This value is already used.``

The message that's displayed when this constraint fails.

em
~~

**type**: ``string``

The name of the entity manager to use for making the query to determine the
uniqueness. If it's left blank, the correct entity manager will determined for
this class. For that reason, this option should probably not need to be
used.