Unable to use resource identifier

The issue

I want to retrieve a resource by its slug thus I’m following the instructions on this page.

I’ve ended up with the following code:

<?php

declare(strict_types=1);

namespace Foo\Lt\Domain\Model\Page;

use ApiPlatform\Core\Annotation\ApiProperty;
use ApiPlatform\Core\Annotation\ApiResource;
use Doctrine\ORM\Mapping as ORM;
use Symfony\Component\Validator\Constraints as Assert;

/**
 * @ORM\Table(name="pages", indexes={@ORM\Index(name="slug_index", columns={"slug"})})
 * @ORM\Entity(repositoryClass="Foo\Infrastructure\Domain\Model\Page\DoctrinePageRepository")
 *
 * @ApiResource(
 *     shortName="Pages",
 *     description="Miscellaneous pages.",
 *     routePrefix="v0",
 *     itemOperations={
 *         "get_page"={
 *              "method"="GET",
 *              "path"="/pages/{slug}",
 *              "requirements"={"slug"="\w+"},
 *              "swagger_context"= {
 *                  "summary"= "Retrieves a page.",
 *                  "description"= "Retrieves a page (i.e. help, terms, privacy)",
 *                  "parameters"= {
 *                      {
 *                          "in"= "path",
 *                          "name"= "slug",
 *                          "type"= "string",
 *                          "example"="help"
 *                      },
 *                  },
 *              },
 *          },
 *     },
 *     collectionOperations={
 *         "get"={"method"="GET"}
 *     },
 *     iri="pages",
 * )
 */
class Page
{
    /**
     * The unique auto incremented primary key.
     *
     * @var int|null
     *
     * @ORM\Id
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue
     */
    protected $id;

    /**
     * The page slug.
     *
     * @var string
     *
     * @ORM\Column(type="string", length=255, nullable=false)
     *
     * @ApiProperty(
     *     identifier=true,
     *     attributes={
     *         "swagger_context"={
     *             "type"="string",
     *             "description"="The page slug.",
     *             "example"="help"
     *         }
     *     },
     * )
     */
    protected $slug;

    /**
     * The page text.
     *
     * @var string
     *
     * @ORM\Column(type="text", nullable=false)
     *
     * @ApiProperty(
     *     attributes={
     *         "swagger_context"={
     *             "type"="string",
     *             "description"="The page text.",
     *             "example"="Foo bar baz",
     *         },
     *     }
     * )
     */
    protected $text;

    public function getId() : int
    {
        return $this->id;
    }

    public function getSlug() : string
    {
        return $this->slug;
    }

    public function getText() : string
    {
        return $this->text;
    }
}

Unfortunately a request to api/v0/pages/help will result in:

{
  "@context": "/api/contexts/Error",
  "@type": "hydra:Error",
  "hydra:title": "An error occurred",
  "hydra:description": "Not found, because of an invalid identifier configuration",
  "trace": [
    {
      "namespace": "",
      "short_class": "",
      "class": "",
      "type": "",
      "function": "",
      "file": "/var/www/app/vendor/api-platform/core/src/EventListener/ReadListener.php",
      "line": 102,
      "args": []
    },

What did not tell anything useful to me, so after removing the try catch from ReadListener the following exception has occurred:

{
  "@context": "/api/contexts/Error",
  "@type": "hydra:Error",
  "hydra:title": "An error occurred",
  "hydra:description": "Parameter \"id\" not found",
  "trace": [
    {
      "namespace": "",
      "short_class": "",
      "class": "",
      "type": "",
      "function": "",
      "file": "/var/www/app/vendor/api-platform/core/src/DataProvider/OperationDataProviderTrait.php",
      "line": 90,
      "args": []
    },

Notes

• I do not need a collectionOperations but I’m declaring one because of this.
• I’m using the iri annotation like suggested here in order to avoid the errors “No collection route associated with the type” and “Unable to generate an IRI for the item of type”
• This issue is kinda messed because at the moment I’ve had a lot of problems trying to configure this simple entity/resource without coupling my domain logic with API Platform.

[gnumoksha]

@soyuka Thanks for answering.

I have some questions:

1. Using “@ApiProperty (identifier = true)” shouldn’t be sufficient to tell the API Platform to use only the slug?
2. Should not this information be described at https://api-platform.com/docs/core/identifiers/?
3. Could you provide an example of how to use a custom controller for this case? I’m still getting “Not Found, because of an invalid identifier configuration”

And, if it is not asking too much, can you provide an example of how to use API platform with only DTOs and serialization? At the moment I do not want to couple my application with the API platform’ way to do things so I only want API Platform to populate a DTO, receive it on a controller and serialize the response.

[soyuka]

It can’t really work like this:

• you’re declaring 2 identifiers (id and slug)
• the route contains slug but Api Platform can’t request your data provider through this
• it’ll try to use the request given id which isn’t in the route params

What you could do is use "path"="/pages/{id} and add a DataProvider that will handle id as a slug. Or do a custom operation with a custom controller.

We don’t have a way to match route params to an identifier like you want it to, I have a proposal here though: https://github.com/api-platform/core/pull/2126. You could maybe add this patch in your stack by overriding some services.