function BookNavigationCacheContext::getCacheableMetadata

File

core/modules/book/src/Cache/BookNavigationCacheContext.php, line 88

Class

BookNavigationCacheContext

Defines the book navigation cache context service.

Namespace

Code

public function getCacheableMetadata() {
  // The book active trail depends on the node and data attached to it.
  // That information is however not stored as part of the node.
  $cacheable_metadata = new CacheableMetadata();
  $node = $this->routeMatch
    ->getParameter('node');
  if ($node instanceof NodeInterface) {
    // If the node is part of a book then we can use the cache tag for that
    // book. If not, then it can't be optimized away.
    if (!empty($node->book['bid'])) {
      $cacheable_metadata->addCacheTags([
        'bid:' . $node->book['bid'],
      ]);
    }
    else {
      $cacheable_metadata->setCacheMaxAge(0);
    }
  }
  return $cacheable_metadata;
}