protected BookExport::exportTraverse(array $tree, $callable)
Traverses the book tree to build printable or exportable output.
During the traversal, the callback is applied to each node and is called recursively for each child of the node (in weight, title order).
Parameters
array $tree: A subtree of the book menu hierarchy, rooted at the current page.
callable $callable: A callback to be called upon visiting a node in the tree.
Return value
string The output generated in visiting each node.
File
- core/modules/book/src/BookExport.php, line 102
Class
- BookExport
- Provides methods for exporting book to different formats.
Namespace
Drupal\book
Code
protected function exportTraverse(array $tree, $callable) {
// If there is no valid callable, use the default callback.
$callable = !empty($callable) ? $callable : array($this, 'bookNodeExport');
$build = array();
foreach ($tree as $data) {
// Note- access checking is already performed when building the tree.
if ($node = $this->nodeStorage->load($data['link']['nid'])) {
$children = $data['below'] ? $this->exportTraverse($data['below'], $callable) : '';
$build[] = call_user_func($callable, $node, $children);
}
}
return $build;
}
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