Handler function cannot have void return type

[AlexSteinerETH]

Hi when i run my script i got this error:

/usr/local/include/crow/middleware.h: In instantiation of ‘typename std::enable_if<crow::black_magic::is_callable<F, crow::request, Args ...>::value>::type crow::detail::wrapped_handler_call(crow::request&, crow::response&, const F&, Args&& ...) [with F = main()::<lambda(const crow::request&)>; Args = {}; typename std::enable_if<crow::black_magic::is_callable<F, crow::request, Args ...>::value>::type = void]’:
/usr/local/include/crow/routing.h:583:47:   required from ‘void crow::TaggedRule<Args>::operator()(Func&&) [with Func = main()::<lambda(const crow::request&)>; Args = {}]’
Run.cpp:55:6:   required from here
/usr/local/include/crow/middleware.h:238:27: error: static assertion failed: Handler function cannot have void return type; valid return types: string, int, crow::response, crow::returnable
  238 |             static_assert(!std::is_same<void, decltype(f(std::declval<crow::request>(), std::declval<Args>()...))>::value,
      |                           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/local/include/crow/middleware.h:241:25: error: invalid use of void expression
  241 |             res = crow::response(f(req, std::forward<Args>(args)...));
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

My code:

#include <iostream>
#include <ctime>
#include <list>


#include <crow.h>

#include "Wallets/Wallets.hpp"
#include "Headers/json.hpp"

using namespace std;
using namespace crow;

Wallets wallets;


int main()
{
    SimpleApp server;

    CROW_ROUTE(server, "/")([]() {
        mustache::context ctx;
        auto main_page = mustache::load("index.html");
        return main_page.render();
    });

    CROW_ROUTE(server, "/wallet").methods("GET"_method)([](const crow::request& req) {
        auto main_page = mustache::load("add_wallet.html");
        return main_page.render();
    });

    CROW_ROUTE(server, "/create-wallet").methods("POST"_method)([](const crow::request& req) {
        cout << endl;

        const Wallet& newWallet = wallets.CreateWallet();

        cout << endl;

        crow::json::wvalue x({{}});
        x["Hash"] = newWallet.wallet_hash;
        x["Phrase"] = newWallet.secret_phrase;

        auto main_page = mustache::load("successfully_wallet_created.html");
        return main_page.render(x);
    });

    CROW_ROUTE(server, "/login").methods("GET"_method)([](const crow::request& req) {
        auto main_page = mustache::load("login_wallet.html");
        return main_page.render();
    });

    
    CROW_ROUTE(server, "/login-wallet").methods("POST"_method)([](const crow::request& req) {
        cout << req.url_params.get("hash") << endl;
    });


    server.port(8080).multithreaded().run();
}

I USE UBUNTU AND I RUN THE CODE WITH :

 #Delete the previous run
rm Run

#Run the server
g++ -std=c++11 Run.cpp -o Run -L /usr/lib/ -lboost_system -lboost_thread -lpthread -ggdb -lz -D CROW_ENABLE_DEBUG $(pkg-config --cflags --libs libmongocxx)

#clear

./Run

Middleware.h

[The-EDev]

your last route takes only a request as argument (meaning the route has to end with return) but you're not returning anything. if you just want to return an OK message to the client, you should do return response();

[AlexSteinerETH]

i just want to return the data of an html input

[The-EDev]

okay, you should add something like return req.url_params.get("hash")

[AlexSteinerETH]

Have this error: (2022-02-17 14:54:57) [ERROR ] An uncaught exception occurred: basic_string::_M_construct null not valid (2022-02-17 14:54:57) [INFO ] Response: 0x7f51540022b0 /login-wallet 500 0

[The-EDev]

could it be that the hash parameter doesn't exist?

[AlexSteinerETH]

I read the documentation, and i used in a wrong way url_params.get(), i just nead to extract data from an html form.

[The-EDev]

html form would probably use multipart, currently it's a little inconvenient to do so but an issue already exists for that (#312) and I'm hoping to implement a PR for it soon.

Let me know if there's anything else related to this you need help with.

[AlexSteinerETH]

Solved, thank you!

I have another question, must I open another issue?

[The-EDev]

Please go ahead, no need to open another issue

[AlexSteinerETH]

Ok, does or will, crow implement ejs?

[The-EDev]

I had to read up on what EJS was, and it seems to be a templating engine built for nodeJS and uses JS syntax. Crow doesn't implement it, it instead uses its own implementation of Mustache to render templates.

From what I currently know about EJS, I'm not sure there's a point to implementing it when Crow has a templating engine.

[AlexSteinerETH]

Ok thats all thank you!