BookBreadcrumbBuilder::build

public BookBreadcrumbBuilder::build(RouteMatchInterface $route_match)

public function build(RouteMatchInterface $route_match) {
  $book_nids = array();
  $breadcrumb = new Breadcrumb();

  $links = array(Link::createFromRoute($this->t('Home'), '<front>'));
  $book = $route_match->getParameter('node')->book;
  $depth = 1;
  // We skip the current node.
  while (!empty($book['p' . ($depth + 1)])) {
    $book_nids[] = $book['p' . $depth];
    $depth++;
  }
  $parent_books = $this->nodeStorage->loadMultiple($book_nids);
  if (count($parent_books) > 0) {
    $depth = 1;
    while (!empty($book['p' . ($depth + 1)])) {
      if (!empty($parent_books[$book['p' . $depth]]) && ($parent_book = $parent_books[$book['p' . $depth]])) {
        $access = $parent_book->access('view', $this->account, TRUE);
        $breadcrumb->addCacheableDependency($access);
        if ($access->isAllowed()) {
          $breadcrumb->addCacheableDependency($parent_book);
          $links[] = Link::createFromRoute($parent_book->label(), 'entity.node.canonical', array('node' => $parent_book->id()));
        }
      }
      $depth++;
    }
  }
  $breadcrumb->setLinks($links);
  $breadcrumb->addCacheContexts(['route.book_navigation']);
  return $breadcrumb;
}