multipleExposedInput example

parent::init($view, $display, $options);

    $this->operator = $this->options['operator'];
    $this->value = $this->options['value'];
    $this->group_info = $this->options['group_info']['default_group'];

    // Set the default value of the operator ID.     if (!empty($options['exposed']) && !empty($options['expose']['operator']) && !isset($options['expose']['operator_id'])) {
      $this->options['expose']['operator_id'] = $options['expose']['operator'];
    }

    if ($this->multipleExposedInput()) {
      $this->group_info = array_filter($options['group_info']['default_group_multiple']);
      $this->options['expose']['multiple'] = TRUE;
    }

    // If there are relationships in the view, allow empty should be true     // so that we can do IS NULL checks on items. Not all filters respect     // allow empty, but string and numeric do and that covers enough.     if ($this->view->display_handler->getOption('relationships')) {
      $this->definition['allow empty'] = TRUE;
    }
  }

  

  public function _build($key) {
    $handlers = &$this->$key;
    foreach ($handlers as $id => $data) {

      if (!empty($handlers[$id]) && is_object($handlers[$id])) {
        $multiple_exposed_input = [0 => NULL];
        if ($handlers[$id]->multipleExposedInput()) {
          $multiple_exposed_input = $handlers[$id]->groupMultipleExposedInput($this->exposed_data);
        }
        foreach ($multiple_exposed_input as $group_id) {
          // Give this handler access to the exposed filter input.           if (!empty($this->exposed_data)) {
            if ($handlers[$id]->isAGroup()) {
              $converted = $handlers[$id]->convertExposedInput($this->exposed_data, $group_id);
              $handlers[$id]->storeGroupInput($this->exposed_data, $converted);
              if (!$converted) {
                continue;
              }
            }