Fid.php

<?php

namespace Drupal\aggregator\Plugin\views\argument;

use Drupal\Core\Entity\EntityTypeManagerInterface;
use Drupal\views\Plugin\views\argument\NumericArgument;
use Symfony\Component\DependencyInjection\ContainerInterface;

/**
 * Argument handler to accept an aggregator feed id.
 *
 * @ingroup views_argument_handlers
 *
 * @ViewsArgument("aggregator_fid")
 */
class Fid extends NumericArgument {
    
    /**
     * The entity type manager.
     *
     * @var \Drupal\Core\Entity\EntityTypeManagerInterface
     */
    protected $entityTypeManager;
    
    /**
     * Constructs a \Drupal\aggregator\Plugin\views\argument\Fid object.
     *
     * @param array $configuration
     *   A configuration array containing information about the plugin instance.
     * @param string $plugin_id
     *   The plugin_id for the plugin instance.
     * @param mixed $plugin_definition
     *   The plugin implementation definition.
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager.
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition, EntityTypeManagerInterface $entity_type_manager) {
        parent::__construct($configuration, $plugin_id, $plugin_definition);
        $this->entityTypeManager = $entity_type_manager;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
        return new static($configuration, $plugin_id, $plugin_definition, $container->get('entity_type.manager'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function titleQuery() {
        $titles = [];
        $feeds = $this->entityTypeManager
            ->getStorage('aggregator_feed')
            ->loadMultiple($this->value);
        foreach ($feeds as $feed) {
            $titles[] = $feed->label();
        }
        return $titles;
    }

}