class HtmlResponsePlaceholderStrategySubscriber

HTML response subscriber to allow for different placeholder strategies.

This allows core and contrib to coordinate how to render placeholders; e.g. an EsiRenderStrategy could replace the placeholders with ESI tags, while e.g. a BigPipeRenderStrategy could store the placeholders in a BigPipe service and render them after the main content has been sent to the client.

Hierarchy

class \Drupal\Core\EventSubscriber\HtmlResponsePlaceholderStrategySubscriber implements \Symfony\Component\EventDispatcher\EventSubscriberInterface

Expanded class hierarchy of HtmlResponsePlaceholderStrategySubscriber

File

core/lib/Drupal/Core/EventSubscriber/HtmlResponsePlaceholderStrategySubscriber.php, line 20

Namespace

Drupal\Core\EventSubscriber

View source

class HtmlResponsePlaceholderStrategySubscriber implements EventSubscriberInterface {
    
    /**
     * The placeholder strategy to use.
     *
     * @var \Drupal\Core\Render\Placeholder\PlaceholderStrategyInterface
     */
    protected $placeholderStrategy;
    
    /**
     * Constructs a HtmlResponsePlaceholderStrategySubscriber object.
     *
     * @param \Drupal\Core\Render\Placeholder\PlaceholderStrategyInterface $placeholder_strategy
     *   The placeholder strategy to use.
     */
    public function __construct(PlaceholderStrategyInterface $placeholder_strategy) {
        $this->placeholderStrategy = $placeholder_strategy;
    }
    
    /**
     * Processes placeholders for HTML responses.
     *
     * @param \Symfony\Component\HttpKernel\Event\ResponseEvent $event
     *   The event to process.
     */
    public function onRespond(ResponseEvent $event) {
        $response = $event->getResponse();
        if (!$response instanceof HtmlResponse) {
            return;
        }
        $attachments = $response->getAttachments();
        if (empty($attachments['placeholders'])) {
            return;
        }
        $attachments['placeholders'] = $this->placeholderStrategy
            ->processPlaceholders($attachments['placeholders']);
        $response->setAttachments($attachments);
    }
    
    /**
     * {@inheritdoc}
     */
    public static function getSubscribedEvents() : array {
        // Run shortly before HtmlResponseSubscriber.
        $events[KernelEvents::RESPONSE][] = [
            'onRespond',
            5,
        ];
        return $events;
    }

}

Members

Title Sort descending	Modifiers	Object type	Summary	Overriden Title
HtmlResponsePlaceholderStrategySubscriber::$placeholderStrategy	protected	property	The placeholder strategy to use.
HtmlResponsePlaceholderStrategySubscriber::getSubscribedEvents	public static	function	Returns an array of event names this subscriber wants to listen to.	Overrides EventSubscriberInterface::getSubscribedEvents
HtmlResponsePlaceholderStrategySubscriber::onRespond	public	function	Processes placeholders for HTML responses.
HtmlResponsePlaceholderStrategySubscriber::__construct	public	function	Constructs a HtmlResponsePlaceholderStrategySubscriber object.