function BookNavigationCacheContext::getCacheableMetadata

Overrides CacheContextInterface::getCacheableMetadata

File

core/modules/book/src/Cache/BookNavigationCacheContext.php, line 75

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.
    $cacheable_metadata = new CacheableMetadata();
    if ($node = $this->requestStack
        ->getCurrentRequest()
        ->get('node')) {
        // If the node is part of a book then we can use the cache tag for that
        // book. If not, then it can't be optimized away.
        if (!empty($node->book['bid'])) {
            $cacheable_metadata->addCacheTags([
                'bid:' . $node->book['bid'],
            ]);
        }
        else {
            $cacheable_metadata->setCacheMaxAge(0);
        }
    }
    return $cacheable_metadata;
}