CategoryListController.php

<?php

/**
 * Definition of Drupal\contact\CategoryListController.
 */
namespace Drupal\contact;

use Drupal\Core\Config\Entity\ConfigEntityListController;
use Drupal\Core\Entity\EntityInterface;

/**
 * Provides a listing of contact categories.
 */
class CategoryListController extends ConfigEntityListController {

  /**
   * Overrides Drupal\Core\Entity\EntityListController::buildHeader().
   */
  public function buildHeader() {
    $row['category'] = t('Category');
    $row['recipients'] = t('Recipients');
    $row['selected'] = t('Selected');
    $row['operations'] = t('Operations');
    return $row;
  }

  /**
   * Overrides Drupal\Core\Entity\EntityListController::buildRow().
   */
  public function buildRow(EntityInterface $entity) {
    $row['category'] = check_plain($entity
      ->label());
    $row['recipients'] = check_plain(implode(', ', $entity->recipients));
    $default_category = config('contact.settings')
      ->get('default_category');
    $row['selected'] = $default_category == $entity
      ->id() ? t('Yes') : t('No');
    $row['operations']['data'] = $this
      ->buildOperations($entity);
    return $row;
  }

}