How to return a response when an exception is thrown?

[drizzle042]

Currently all Drogon does is log the exception using trantor’s logger. But I don’t know how to send a response for a particular exception.

[Iamnotagenius]

Set a custom exception handler before .run() like so:

drogon::app().setExceptionHandler(myExceptionHandler);

Here's how you define one:

void myExceptionHandler(const std::exception& e, 
                        const drogon::HttpRequestPtr& req, 
                        std::function<void (const drogon::HttpResponsePtr &)>&& callback) {
    if (dynamic_cast<const SomeException*>(&e) != nullptr) {
        callback(errorResponse(drogon::k400BadRequest, e.what()));
        return;
    }
    LOG_ERROR << "Unhandled exception: " << e.what();
    callback(errorResponse(drogon::k500InternalServerError, "Unexpected error"));
}