Basic Constraints and Options¶

Adding a validation constraint is easy. To make the username field required, add @Assert\NotBlank above the property:

// src/Yoda/UserBundle/Entity/User.php
// ...

/**
 * @ORM\Column(name="username", type="string", length=255)
 * @Assert\NotBlank()
 */
private $username;

Try it out! When we submit the form blank, we see the validation error above the field. It looks terrible, but we’ll work on that later. To customize the message, add the message option:

// src/Yoda/UserBundle/Entity/User.php
// ...

/**
 * @ORM\Column(name="username", type="string", length=255)
 * @Assert\NotBlank(message="Put in a username you rebel scum :P")
 */
private $username;

Refresh to see the new error.

All of this magic happens automatically when we call handleRequest in our controller. This takes the submitted values, pushes them into the User object, and then applies validation.

Add all the Constraints!¶

Let’s keep going. We can use the Length constraint to make sure the username is at least 3 characters long:

/**
 * @ORM\Column(name="username", type="string", length=255)
 * @Assert\NotBlank(message="Put in a username of course!")
 * @Assert\Length(min=3, minMessage="Give us at least 3 characters!")
 */
private $username;

For the email property, use NotBlank and Email to guarantee that it’s a valid email address:

/**
 * @ORM\Column(type="string", length=255)
 * @Assert\NotBlank
 * @Assert\Email
 */
private $email;

For plainPassword, we can use the NotBlank constraint and the Regex constraint to guarantee a strong password:

/**
 * @Assert\NotBlank
 * @Assert\Regex(
 *      pattern="/^(?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?!.*\s).*$/",
 *      message="Use 1 upper case letter, 1 lower case letter, and 1 number"
 * )
 */
private $plainPassword;

Let’s try this out by filling out the form in different ways. All the errors show up! They’re just really ugly.

Docs for The Built-In Constraints¶

Symfony comes packed with a lot of other constraints you can use. Check them out in the reference section of the documentation. You can see the Length constraint we just used and all of the options for it. Cool!

The UniqueEntity Constraint¶

Check out the UniqueEntity constraint. This is useful if you need to make sure a value stays unique in the database. We need to make sure that nobody signs up using an existing username or email address, so this is perfect.

The UniqueEntity constraint is special because unlike the others, this one requires a different use statement. Copy it into your User class. Also, @UniqueEntity goes above the class, not above a property. It takes two options: the field that should be unique followed by a message. Add a constraint for both the username and the email:

// src/Yoda/UserBundle/Entity/User.php
// ...

use Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity;

/**
 * @ORM\Table(name="yoda_user")
 * @ORM\Entity(repositoryClass="Yoda\UserBundle\Entity\UserRepository")
 * @UniqueEntity(fields="username", message="That username is taken!")
 * @UniqueEntity(fields="email", message="That email is taken!")
 */
class User implements AdvancedUserInterface, Serializable

If we try to register with an existing username or email, we see the error!

The Callback Constraint¶

Before we move on, I want to show you one more useful constraint: Callback. This constraint is awesome because it lets you create a method inside your class that’s called during validation. You can apply whatever logic you need to figure out if the object is valid. You can even place the errors on exactly which field you want. If you have a more difficult validation problem, this might be exactly what you need.

We won’t show it here, but check it out.