farm-2.x-dev/modules/core/quantity/src/EventSubscriber/MapRenderEventSubscriber.php

<?php

namespace Drupal\quantity\EventSubscriber;

use Drupal\Core\Config\ConfigFactoryInterface;
use Drupal\farm_map\Event\MapRenderEvent;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;

/**
 * An event subscriber for the MapRenderEvent.
 *
 * Adds the quantity.system_of_measurement setting to maps.
 */
class MapRenderEventSubscriber implements EventSubscriberInterface {

  /**
   * The config factory service.
   *
   * @var \Drupal\Core\Config\ConfigFactoryInterface
   */
  private $configFactory;

  /**
   * Constructor.
   *
   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
   *   The config factory service.
   */
  public function __construct(ConfigFactoryInterface $config_factory) {
    $this->configFactory = $config_factory;
  }

  /**
   * {@inheritdoc}
   */
  public static function getSubscribedEvents() {
    return [
      MapRenderEvent::EVENT_NAME => 'onMapRender',
    ];
  }

  /**
   * React to the MapRenderEvent.
   *
   * @param \Drupal\farm_map\Event\MapRenderEvent $event
   *   The MapRenderEvent.
   *
   * @throws \Drupal\Component\Plugin\Exception\InvalidPluginDefinitionException
   * @throws \Drupal\Component\Plugin\Exception\PluginNotFoundException
   */
  public function onMapRender(MapRenderEvent $event) {

    // Set a cache tag on the quantity settings in case this ever changes.
    $event->addCacheTags(['config:quantity.settings']);

    // Add the system of measurement to drupalSettings.farm_map.units.
    $measurement = $this->configFactory->get('quantity.settings')->get('system_of_measurement');
    $event->element['#attached']['drupalSettings']['farm_map']['units'] = $measurement;
  }

}