public function save_data($post_id)
 {
     global $post;
     if (is_object($post) && self::CPT_NAME !== $post->post_type) {
         return;
     }
     $input = new SpectrOMInput();
     // TODO: nonce verification
     $form_data = $_POST['spectrom_metabox'];
     $this->_create_settings($post_id);
     $valid = new SpectrOMValidation();
     if ($valid->validate_all($this->_settings, $form_data)) {
         // save meta data
     }
 }