How to validate unique entities in an entity collection in symfony2

Question

I have an entity with a OneToMany relation to another entity, when I persist the parent entity I want to ensure the children contain no duplicates.

Here's the classes I have been using, the discounts collection should not contain two products with the same name for a given client.

I have a Client entity with a collection of discounts:

/**
 * @ORM\Entity
 */
class Client {

    /**
     * @ORM\Id
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    protected $id;

    /**
     * @ORM\Column(type="string", length=128, nullable="true")
     */
    protected $name;

    /**
     * @ORM\OneToMany(targetEntity="Discount", mappedBy="client", cascade={"persist"}, orphanRemoval="true")
     */
    protected $discounts;

}

/**
 * @ORM\Entity
 * @UniqueEntity(fields={"product", "client"}, message="You can't create two discounts for the same product")
 */
    class Discount {
        /**
         * @ORM\Id
         * @ORM\Column(type="string", length=128, nullable="true")
         */
        protected $product;

        /**
         * @ORM\Id
         * @ORM\ManyToOne(targetEntity="Client", inversedBy="discounts")
         * @ORM\JoinColumn(name="client_id", referencedColumnName="id")
         */
        protected $client;

        /**
         * @ORM\Column(type="decimal", scale=2)
         */
        protected $percent;
    }

I tried using UniqueEntity for the Discount class as you can see, the problem is that it seems the validator only checks what's loaded on the database (which is empty), so when the entities are persisted I get a "SQLSTATE[23000]: Integrity constraint violation".

I have checked the Collection constraint buy it seems to handle only collections of fields, not entities.

There's also the All validator, which lets you define constraints to be applied for each entity, but not to the collection as a whole.

I need to know if there are entity collection constraints as a whole before persisting to the database, other than writing a custom validator or writing a Callback validator each time.

Answer 1

I've created a custom constraint/validator for this.

It validates a form collection using the "All" assertion, and takes an optional parameter : the property path of the property to check the entity equality.

(it's for Symfony 2.1, to adapt it to Symfony 2.0 check the end of the answer) :

For more information on creating custom validation constraints, check The Cookbook

The constraint :

#src/Acme/DemoBundle/Validator/constraint/UniqueInCollection.php
<?php

namespace Acme\DemoBundle\Validator\Constraint;

use Symfony\Component\Validator\Constraint;

/**
* @Annotation
*/
class UniqueInCollection extends Constraint
{
    public $message = 'The error message (with %parameters%)';
    // The property path used to check wether objects are equal
    // If none is specified, it will check that objects are equal
    public $propertyPath = null;
}

And the validator :

#src/Acme/DemoBundle/Validator/constraint/UniqueInCollectionValidator.php
<?php

namespace Acme\DemoBundle\Validator\Constraint;

use Symfony\Component\Validator\Constraint;
use Symfony\Component\Validator\ConstraintValidator;
use Symfony\Component\Form\Util\PropertyPath;

class UniqueInCollectionValidator extends ConstraintValidator
{

    // We keep an array with the previously checked values of the collection
    private $collectionValues = array();

    // validate is new in Symfony 2.1, in Symfony 2.0 use "isValid" (see below)
    public function validate($value, Constraint $constraint)
    {
        // Apply the property path if specified
        if($constraint->propertyPath){
            $propertyPath = new PropertyPath($constraint->propertyPath);
            $value = $propertyPath->getValue($value);
        }

        // Check that the value is not in the array
        if(in_array($value, $this->collectionValues))
            $this->context->addViolation($constraint->message, array());

        // Add the value in the array for next items validation
        $this->collectionValues[] = $value;
    }
}

In your case, you would use it like this :

use Acme\DemoBundle\Validator\Constraints as AcmeAssert;

// ...

/**
 * @ORM\OneToMany(targetEntity="Discount", mappedBy="client", cascade={"persist"}, orphanRemoval="true")
 * @Assert\All(constraints={
 *     @AcmeAssert\UniqueInCollection(propertyPath ="product")
 * })
 */

For Symfony 2.0, change the validate function by :

public function isValid($value, Constraint $constraint)
{
        $valid = true;

        if($constraint->propertyPath){
            $propertyPath = new PropertyPath($constraint->propertyPath);
            $value = $propertyPath->getValue($value);
        }

        if(in_array($value, $this->collectionValues)){
            $valid = false;
            $this->setMessage($constraint->message, array('%string%' => $value));
        }

        $this->collectionValues[] = $value;

        return $valid

}

Answer 2

Here is a version working with multiple fields just like UniqueEntity does. Validation fails if multiple objects have same values.

Usage:

/**
* ....
* @App\UniqueInCollection(fields={"name", "email"})
*/
private $contacts;
//Validation fails if multiple contacts have same name AND email

The constraint class ...

<?php
namespace App\Validator\Constraints;

use Symfony\Component\Validator\Constraint;

/**
 * @Annotation
 */
class UniqueInCollection extends Constraint
{
    public $message = 'Entry is duplicated.';
    public $fields;

    public function validatedBy()
    {
        return UniqueInCollectionValidator::class;
    }
}

The validator itself ....

<?php

namespace App\Validator\Constraints;

use Symfony\Component\PropertyAccess\PropertyAccess;
use Symfony\Component\Validator\Constraint;
use Symfony\Component\Validator\ConstraintValidator;
use Symfony\Component\Validator\Exception\UnexpectedTypeException;
use Symfony\Component\Validator\Exception\UnexpectedValueException;

class UniqueInCollectionValidator extends ConstraintValidator
{
    /**
     * @var \Symfony\Component\PropertyAccess\PropertyAccessor
     */
    private $propertyAccessor;

    public function __construct()
    {
        $this->propertyAccessor = PropertyAccess::createPropertyAccessor();
    }

    /**
     * @param mixed $collection
     * @param Constraint $constraint
     * @throws \Exception
     */
    public function validate($collection, Constraint $constraint)
    {
        if (!$constraint instanceof UniqueInCollection) {
            throw new UnexpectedTypeException($constraint, UniqueInCollection::class);
        }

        if (null === $collection) {
            return;
        }

        if (!\is_array($collection) && !$collection instanceof \IteratorAggregate) {
            throw new UnexpectedValueException($collection, 'array|IteratorAggregate');
        }

        if ($constraint->fields === null) {
            throw new \Exception('Option propertyPath can not be null');
        }

        if(is_array($constraint->fields)) $fields = $constraint->fields;
        else $fields = [$constraint->fields];


        $propertyValues = [];
        foreach ($collection as $key => $element) {
            $propertyValue = [];
            foreach ($fields as $field) {
                $propertyValue[] = $this->propertyAccessor->getValue($element, $field);
            }


            if (in_array($propertyValue, $propertyValues, true)) {

                $this->context->buildViolation($constraint->message)
                    ->atPath(sprintf('[%s]', $key))
                    ->addViolation();
            }

            $propertyValues[] = $propertyValue;
        }

    }
}