如何从上下文筛选器中通过父项过滤公开筛选器中的子项？

Question

我有一个带有嵌套分类法术语的区域词汇表，如下所示。

我对Drupal 8中的分类法术语有一个视图，它对父和子的所有术语都有一个公开的过滤器。我想要的是，当我添加术语父级的上下文过滤器时，exposed过滤器应该只显示与上下文过滤器中父项匹配的子术语。

例如，如果URL包含Deoghar，那么公开的过滤器(如下面的filter)应该只显示术语Karon作为选项。

Answer 1

我最近在我的一个使用MYMODULE_form_views_exposed_form_alter的项目中做了这件事。代码假设在第一个位置上有一个带有术语ID的视图作为上下文过滤器，例如domain.com/myview/123

getStorage('view');
  $display_id = $view['view']->current_display;

  if ($form_id == 'views_exposed_form' && $view['view']->id() == 'MY_VIEW' && $display_id == 'MY_VIEWDISPLAY') {
    if (!empty($view['view']->args) && $view['view']->args[0]) {
      //get the term ID from the contextual filter
      $contextTermId = $view['view']->args[0];
      $entriesToRemove = [];

      $currentFilterValue = $form_state->getUserInput()['FIELD_FILTER_TAXONOMY'];
      foreach ($form['FIELD_FILTER_TAXONOMY']['#options'] as $idx => $entry) {
        if ($idx === 'All') {
          //remove the old root '- Any -' option
          $entriesToRemove[] = $idx;
        }
        //the next line is a bit shaky might need rework:
        //sometimes filter entries are a stdClass, 
        //but I've also seen entries as array in other exposed forms (grouped filters?)
        elseif ($entry instanceof stdClass && is_array($entry->option)) {
          $termId = key($entry->option);
          $termName = current($entry->option);
          //the context filter term is our new root, so we change its label to '- Any -'
          if ($termId == $contextTermId) {
            $form['FIELD_FILTER_TAXONOMY']['#options'][$idx]->option = [$termId => t('- Any -')];
            if (empty($currentFilterValue) || $currentFilterValue == 'All') {
              //we've removed the default empty/All entry, reset it to our newly created, faked '- Any -' category
              $form_state->setUserInput(['FIELD_FILTER_TAXONOMY' => $contextTermId]);
            }
          }
          else {
            //this is the core part: for each filter option load the term
            //and check if it is a child of the contextual filter term
            $parents = \Drupal::entityTypeManager()
              ->getStorage('taxonomy_term')
              ->loadParents($termId);
            if (!in_array($contextTermId, array_keys($parents))) {
              $entriesToRemove[] = $idx;
            }
            else {
              //optional: we are in a sub-filter now,so we no longer need the leading '-' to indicate hierarchy
              $form['FIELD_FILTER_TAXONOMY']['#options'][$idx]->option = [$termId => trim(preg_replace('/^-/', '', $termName))];
            }
          }
        }
      }
      foreach ($entriesToRemove as $idx) {
        unset($form['FIELD_FILTER_TAXONOMY']['#options'][$idx]);
      }
      //optional: if there is only 1 entry left, hide the filter
      if (count($form['FIELD_FILTER_TAXONOMY']['#options']) == 1) {
        $form['FIELD_FILTER_TAXONOMY'] = [
          '#type' => 'hidden',
          'value' => $contextTermId
        ];
      }
    }
  }
}

注意:不要在庞大的分类法上这样做，我的代码加载每个分类法术语来决定是否需要删除它。

Answer 2

正如@Hudri所说，您可以使用MYMODULE_form_views_exposed_form_alter()修改表单。

与其检查每个术语是否是上下文筛选器参数，不如使用TermStorage::loadTree()方法加载术语下的术语树。

$vocabulary_id = 'tags';
// Get this from your view object's contextual argument, e.g. $view->args[0], etc
$parent_id = 11;

$child_terms = \Drupal::entityTypeManager()
  ->getStorage('taxonomy_term')
  ->loadTree($vocabulary_id, $parent_id);

// Next build an options array of the child terms.
$child_term_options = [];
// Maybe you want an Any option
$child_term_options[''] = '- Any -';
foreach ($child_terms as $term) {
  $child_term_options[$term->tid] = $term->name;       
}

// Next update your filter options with only the child terms:
$form['MY_EXPOSED_FILTER']['#options'] = $child_term_options;