ParamConverterSubscriber.php

<?php

namespace Drupal\Core\EventSubscriber;

use Drupal\Core\ParamConverter\ParamConverterManagerInterface;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Drupal\Core\Routing\RoutingEvents;
use Drupal\Core\Routing\RouteBuildEvent;

/**
 * Event subscriber for registering parameter converters with routes.
 */
class ParamConverterSubscriber implements EventSubscriberInterface {
    
    /**
     * The parameter converter manager.
     *
     * @var \Drupal\Core\ParamConverter\ParamConverterManagerInterface
     */
    protected $paramConverterManager;
    
    /**
     * Constructs a new ParamConverterSubscriber.
     *
     * @param \Drupal\Core\ParamConverter\ParamConverterManagerInterface $param_converter_manager
     *   The parameter converter manager that will be responsible for upcasting
     *   request attributes.
     */
    public function __construct(ParamConverterManagerInterface $param_converter_manager) {
        $this->paramConverterManager = $param_converter_manager;
    }
    
    /**
     * Applies parameter converters to route parameters.
     *
     * @param \Drupal\Core\Routing\RouteBuildEvent $event
     *   The event to process.
     */
    public function onRoutingRouteAlterSetParameterConverters(RouteBuildEvent $event) {
        $this->paramConverterManager
            ->setRouteParameterConverters($event->getRouteCollection());
    }
    
    /**
     * {@inheritdoc}
     */
    public static function getSubscribedEvents() : array {
        // Run after \Drupal\system\EventSubscriber\AdminRouteSubscriber.
        $events[RoutingEvents::ALTER][] = [
            'onRoutingRouteAlterSetParameterConverters',
            -220,
        ];
        return $events;
    }

}