public function addValidator($index, $method = null, array $params = [], $message = null)
    {
        // set up params
        array_unshift($params, $method);
        array_unshift($params, $index);

        call_user_func_array([$this->getValidator(), 'addRule'], $params);

        // Message management
        if (!is_null($message)) {
            $this->getValidator()->addMessage($index, $message);
        }

        return $this;
    }