Tableselect::preRenderTableselect

public static Tableselect::preRenderTableselect($element)

    $options = array(
      array(
        'title' => $this->t('How to Learn Drupal'),
        'content_type' => $this->t('Article'),
        'status' => 'published',
        '#attributes' => array('class' => array('article-row')),
      ),
      array(
        'title' => $this->t('Privacy Policy'),
        'content_type' => $this->t('Page'),
        'status' => 'published',
        '#attributes' => array('class' => array('page-row')),
      ),
    );
    $header = array(
      'title' => $this->t('Title'),
      'content_type' => $this->t('Content type'),
      'status' => $this->t('Status'),
    );
    $form['table'] = array(
      '#type' => 'tableselect',
      '#header' => $header,
      '#options' => $options,
      '#empty' => $this->t('No content available.'),
    );
  

public static function preRenderTableselect($element) {
  $rows = array();
  $header = $element['#header'];
  if (!empty($element['#options'])) {
    // Generate a table row for each selectable item in #options.
    foreach (Element::children($element) as $key) {
      $row = array();

      $row['data'] = array();
      if (isset($element['#options'][$key]['#attributes'])) {
        $row += $element['#options'][$key]['#attributes'];
      }
      // Render the checkbox / radio element.
      $row['data'][] = drupal_render($element[$key]);

      // As table.html.twig only maps header and row columns by order, create
      // the correct order by iterating over the header fields.
      foreach ($element['#header'] as $fieldname => $title) {
        // A row cell can span over multiple headers, which means less row
        // cells than headers could be present.
        if (isset($element['#options'][$key][$fieldname])) {
          // A header can span over multiple cells and in this case the cells
          // are passed in an array. The order of this array determines the
          // order in which they are added.
          if (is_array($element['#options'][$key][$fieldname]) && !isset($element['#options'][$key][$fieldname]['data'])) {
            foreach ($element['#options'][$key][$fieldname] as $cell) {
              $row['data'][] = $cell;
            }
          }
          else {
            $row['data'][] = $element['#options'][$key][$fieldname];
          }
        }
      }
      $rows[] = $row;
    }
    // Add an empty header or a "Select all" checkbox to provide room for the
    // checkboxes/radios in the first table column.
    if ($element['#js_select']) {
      // Add a "Select all" checkbox.
      $element['#attached']['library'][] = 'core/drupal.tableselect';
      array_unshift($header, array('class' => array('select-all')));
    }
    else {
      // Add an empty header when radio buttons are displayed or a "Select all"
      // checkbox is not desired.
      array_unshift($header, '');
    }
  }

  $element['#header'] = $header;
  $element['#rows'] = $rows;

  return $element;
}