Crow/examples/example_vs.cpp

#define CROW_MAIN
#include "crow.h"

#include <sstream>

class ExampleLogHandler : public crow::ILogHandler {
    public:
        void log(std::string message, crow::LogLevel level) override {
//            cerr << "ExampleLogHandler -> " << message;
        }
};

struct ExampleMiddleware 
{
    std::string message;

    ExampleMiddleware() : message("foo")
    {
    }

    void setMessage(const std::string &newMsg)
    {
        message = newMsg;
    }

    struct context
    {
    };

    void before_handle(crow::request& req, crow::response& res, context& ctx)
    {
        CROW_LOG_DEBUG << " - MESSAGE: " << message;
    }

    void after_handle(crow::request& req, crow::response& res, context& ctx)
    {
        // no-op
    }
};

int main()
{
    crow::App<ExampleMiddleware> app;

    app.get_middleware<ExampleMiddleware>().setMessage("hello");

    CROW_ROUTE(app, "/")
        .name("hello")
    ([]{
        return "Hello World!";
    });

    CROW_ROUTE(app, "/about")
    ([](){
        return "About Crow example.";
    });

    // a request to /path should be forwarded to /path/
    CROW_ROUTE(app, "/path/")
    ([](){
        return "Trailing slash test case..";
    });

    // simple json response
    CROW_ROUTE(app, "/json")
    ([]{
        crow::json::wvalue x;
        x["message"] = "Hello, World!";
        return x;
    });

    CROW_ROUTE(app, "/hello/<int>")
    ([](int count){
        if (count > 100)
            return crow::response(400);
        std::ostringstream os;
        os << count << " bottles of beer!";
        return crow::response(os.str());
    });

    CROW_ROUTE(app, "/add/<int>/<int>")
    ([](crow::response& res, int a, int b){
        std::ostringstream os;
        os << a+b;
        res.write(os.str());
        res.end();
    });

    // Compile error with message "Handler type is mismatched with URL paramters"
    //CROW_ROUTE(app,"/another/<int>")
    //([](int a, int b){
        //return crow::response(500);
    //});

    // more json example
    CROW_ROUTE(app, "/add_json")
        .methods(crow::HTTPMethod::Post)
    ([](const crow::request& req){
        auto x = crow::json::load(req.body);
        if (!x)
            return crow::response(400);
        auto sum = x["a"].i()+x["b"].i();
        std::ostringstream os;
        os << sum;
        return crow::response{os.str()};
    });

    app.route_dynamic("/params")
    ([](const crow::request& req){
        std::ostringstream os;
        os << "Params: " << req.url_params << "\n\n"; 
        os << "The key 'foo' was " << (req.url_params.get("foo") == nullptr ? "not " : "") << "found.\n";
        if(req.url_params.get("pew") != nullptr) {
            double countD = boost::lexical_cast<double>(req.url_params.get("pew"));
            os << "The value of 'pew' is " <<  countD << '\n';
        }
        auto count = req.url_params.get_list("count");
        os << "The key 'count' contains " << count.size() << " value(s).\n";
        for(const auto& countVal : count) {
            os << " - " << countVal << '\n';
        }
        return crow::response{os.str()};
    });    

    // ignore all log
    crow::logger::setLogLevel(crow::LogLevel::Debug);
    //crow::logger::setHandler(std::make_shared<ExampleLogHandler>());

    app.port(18080)
        .multithreaded()
        .run();
}

Edit example_vs.cpp to use CROW_ROUTE instead of app.route_dynamic.

    VS2019 error:
    '<function-style-cast>': cannot convert from 'void' to 'crow::response'