How to load the immediate parent link in a preprocess function?

Question

I am using menu block to show a section of the navigation. I have a requirement to show the parent link at the top, but that would not gel with the menu configuration.

Therefore, I should be able to solve this by taking the first link in the list, and loading the parent. Then, I want to add that as a variable, and render it in my twig file above the loop that would output the entire link tree. However, I am coming up short on how to do this effectively.

So far, I have:

function mytheme_preprocess_block__menu_block(&$variables) {
  if ($variables['elements']['#id'] == 'left_navigation' && !empty($variables['elements']['content']['#items'])) {
    $children = $variables['elements']['content']['#items'];
    $top_child = key($children);

    $menu_link_manager = \Drupal::service('plugin.manager.menu.link');
    $menu_link_parents = $menu_link_manager->getParentIds($top_child);

    // the one we want should be the second one. the first one is the one in the main navigation across the top.
    $parent = end($menu_link_parents);
    $parent = str_replace('menu_link_content:', '' , $parent);
    $menu_content = current(\Drupal::entityTypeManager()->getStorage('menu_link_content')->loadByProperties(array('uuid' => $parent)));

    $variables['top_parent'] = [
      'title' => $menu_content->getTitle(),
      'url' => $menu_content->getUrlObject()
    ];
  }
}

I am lost at the point I retrieve the parent. Is there a way to get the UUID instead of the dirty str_replace? Also, how can I take that UUID, and create an object similar to menu items that would be rendered?

Answer 1

I think you can do it with the 'plugin.manager.menu.link' service:

$link = $this->menuActiveTrail->getActiveLink();

if(!empty($link->getParent())) {
  $parent_link = Drupal::service('plugin.manager.menu.link')->createInstance($link->getParent());
  $menu_item = MenuLinkContent::load($parent_link->getMetaData()['entity_id']);
}

This way you don't have to replace the prefix.