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/ApiResource/Person.php with Symfony or app/ApiResource/Person.php with Laravel
namespace App\ApiResource;

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
# The YAML syntax is only supported for Symfony
properties:
  App\ApiResource\Person:
    code:
      identifier: true
resource:
  App\ApiResource\Person:
    provider: App\State\PersonProvider

<!-- The XML syntax is only supported for Symfony -->
<properties xmlns="https://api-platform.com/schema/metadata/properties-3.0">
    <property resource="App\ApiResource\Person" name="code" identifier="true"/>
</properties>
<resources xmlns="https://api-platform.com/schema/metadata/resources-3.0">
    <resource class="App\ApiResource\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 resource:

<?php
// api/src/State/PersonProvider.php with Symfony or app/State/PersonProvider.php with Laravel

namespace App\State;

use App\ApiResource\Person;
use ApiPlatform\Metadata\Operation;
use ApiPlatform\State\ProviderInterface;
use App\Uuid;

/**
 * @implements ProviderInterface<Person>
 */
final class PersonProvider implements ProviderInterface
{
    public function provide(Operation $operation, array $uriVariables = [], array $context = []): Person
    {
        // 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
// api/src/Identifier/UuidUriVariableTransformer.php with Symfony or app/Identifier/UuidUriVariableTransformer.php with Laravel 
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 $context = []): Uuid
     {
        try {
            return Uuid::fromString($value);
        } 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 $context = []): bool
    {
        foreach ($types as $type) {
            if (is_a($type, Uuid::class, true)) {
                return true;
            }
        }

        return false;
    }
}

Tag this service as an api_platform.uri_variables.transformer using one of the configurations below:

# Tag the Service using Symfony

# api/config/services.yaml
# The YAML syntax is only supported for Symfony

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

<!-- The XML syntax is only supported for Symfony -->

  <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!

# Tag the Service using Laravel

<?php

namespace App\Providers;

use App\Identifier\UuidUriVariableTransformer;
use ApiPlatform\Metadata\UriVariableTransformerInterface;
use Illuminate\Support\ServiceProvider;

class AppServiceProvider extends ServiceProvider
{
    public function register(): void
    {
        $this->app->tag([UuidUriVariableTransformer::class], UriVariableTransformerInterface::class);
    }
}

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)
\Stringable (essential when using composite identifiers from related resource classes)