# Identifiers

Every item operation has an identifier in its URL. Although this identifier is usually a number, it can also be an UUID, a date, or the type of your choice. To help with your development experience, we introduced an identifier normalization process.

# Custom Identifier Normalizer

In the following chapter, we’re assuming that App\Uuid is a project-owned class that manages a time-based UUID.

Let’s say you have the following class, which is identified by a UUID type. In this example, UUID is not a simple string but an object with many attributes.

<?php
// api/src/Entity/Person.php
namespace App\Entity;

use ApiPlatform\Metadata\ApiProperty;
use ApiPlatform\Metadata\ApiResource;
use App\State\PersonProvider;
use App\Uuid;

#[ApiResource(provider: PersonProvider::class)]
final class Person
{
    /**
     * @var Uuid
     */
    #[ApiProperty(identifier: true)]
    public $code;
    
    // ...
}

# api/config/api_platform/resources/Person.yaml
properties:
    App\Entity\Person:
        code:
            identifier: true
resource:
    App\Entity\Person:
        provider: App\State\PersonProvider

<properties xmlns="https://api-platform.com/schema/metadata/properties-3.0">
    <property resource="App\Entity\Person" name="code" identifier="true"/>
</properties>
<resources xmlns="https://api-platform.com/schema/metadata/resources-3.0">
    <resource class="App\Entity\Person" provider="App\State\PersonProvider" />
</resources>

Once registered as an ApiResource, having an existing person, it will be accessible through the following URL: /people/110e8400-e29b-11d4-a716-446655440000. Note that the property identifying our resource is named code.

Let’s create a Provider for the Person entity:

<?php
namespace App\State;

use App\Entity\Person;
use ApiPlatform\State\ProviderInterface;
use App\Uuid;

final class PersonProvider implements ProviderInterface
{
    /**
     * {@inheritDoc}
     */
    public function provide(Operation $operation, array $uriVariables = [], array $context = [])
    {
        // Our identifier is:
        // $uriVariables['code']
        // although it's a string, it's not an instance of Uuid and we wanted to retrieve the timestamp of our time-based uuid:
        // $uriVariable['code']->getTimestamp()
    }
}

To cover this use case, we need to transform the identifier to an instance of our App\Uuid class. This case is covered by an URI variable transformer:

<?php
namespace App\Identifier;

use ApiPlatform\Api\UriVariableTransformerInterface;
use ApiPlatform\Exception\InvalidUriVariableException;
use App\Uuid;

final class UuidUriVariableTransformer implements UriVariableTransformerInterface
{
    /**
     * Transforms a uri variable value.
     *
     * @param mixed $value   The uri variable value to transform
     * @param array $types   The guessed type behind the uri variable
     * @param array $context Options available to the transformer
     *
     * @throws InvalidUriVariableException Occurs when the uriVariable could not be transformed
     */
     public function transform($value, array $types, array $context = []) {
        try {
            return Uuid::fromString($data);
        } catch (InvalidUuidStringException $e) {
            throw new InvalidUriVariableException($e->getMessage());
        }
     }

    /**
     * Checks whether the given uri variable is supported for transformation by this transformer.
     *
     * @param mixed $value   The uri variable value to transform
     * @param array $types   The types to which the data should be transformed
     * @param array $context Options available to the transformer
     */
    public function supportsTransformation($value, array $types, array $context = []): bool
    {
        return is_a($type, Uuid::class, true);
    }
}

Tag this service as an api_platform.uri_variables.transformer:

services:
    App\Identifier\UuidUriVariableTransformer:
        tags:
            - { name: api_platform.uri_variables.transformer }

  <service id="App\Identifier\UuidUriVariableTransformer" class="App\Identifier\UuidUriVariableTransformer" public="false">
      <tag name="api_platform.uri_variables.transformer" />
  </service>

Your PersonProvider will now work as expected!

# Changing Identifier in a Doctrine Entity

If your resource is also a Doctrine entity and you want to use another identifier other than the Doctrine one, you have to unmark it:

<?php
// api/src/Entity/Person.php
namespace App\Entity;

use ApiPlatform\Metadata\ApiProperty;
use ApiPlatform\Metadata\ApiResource;
use App\Uuid;
use Doctrine\ORM\Mapping as ORM;

#[ORM\Entity]
#[ApiResource]
final class Person
{
    #[ORM\Id, ORM\Column, ORM\GeneratedValue]
    #[ApiProperty(identifier: false)]
    private ?int $id = null;
    
    /**
     * @var Uuid
     */
    #[ORM\Column(type: 'uuid', unique: true)]
    #[ApiProperty(identifier: true)]
    public $code;
    
    // ...
}

# Supported Identifiers

API Platform supports the following identifier types:

scalar (string, integer)
\DateTime (uses the symfony DateTimeNormalizer internally, see DateTimeIdentifierNormalizer)
\Ramsey\Uuid\Uuid (see UuidNormalizer)
\Symfony\Component\Uid\Ulid (see UlidNormalizer)
\Symfony\Component\Uid\Uuid (see UuidNormalizer)

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# Identifiers

# Custom Identifier Normalizer

# Changing Identifier in a Doctrine Entity

# Supported Identifiers