/** * Validate data. * * This ensures that key file is provided if URL is provided. * * @param string $data * @return mixed True on success, else error message. */ public function validate($data) { $result = parent::validate($data); if ($result !== true) { return $result; } $usercontext = context_user::instance($USER->id); $url = get_config('filter_cloudfront_signurl', 'distributionurl'); $fs = get_file_storage(); if ($url != '' && empty($data)) { return get_string('errornoprivatekey', 'filter_cloudfront_signurl'); } return true; }