public function toResponse($request)
    {
        if(! $this->handler && ! is_callable($this->handler)) {
            throw new ErrorException("No handler set");
        }

        $parameters = array_merge(
            [$request, $this->action],
            $this->parameters
        );

        try {
            $payload = call_user_func_array($this->handler, array_values($parameters));
        }
        catch (Exception $e) {
            // We'll assume that if an Exception has an error code 
            // that is explicitly defined, we want to use it as an
            // HTTP error code. if not we'll just let the 
            // Exception handler takes care of it. 
            $code = $e->getCode();

            if (! $this->isValidHttpStatusCode($code)) {
                throw $e;
            }
            
            $this->setStatusCode($code);

            return $e instanceof HasMessageBag 
                ? $this->respondWithMessageBag($e->getMessageBag(), class_basename($e))
                : $this->respondWithError($e->getMessage(), class_basename($e));
        }   
        catch (ValidationException $e) {
            throw $e;
        }

        return $this->handlePayload($payload);
    }