lambdas.cpp

void setupRouting() {
    registerRoute("/api/furnace", HTTP_GET, [&] (Request& request) {
        furnaceController.apiGetAction(request);
    });
    /* and many more like this one */
}

// OPTION A: copy callback to function + move to lambda
void registerRoute(
    const char* const uri,
    const HttpMethod method,
    std::function<void(Request& request)> callback
) {
    server.on(uri, method, [&, callback = std::move(callback)] (Request* const request) {
        /* some stuff here */

        callback(*request);
    });
}

// OPTION B: reference callback to function + copy to lambda
void registerRoute(
    const char* const uri,
    const HttpMethod method,
    const std::function<void(Request& request)>& callback
) {
    server.on(uri, method, [&, callback] (Request* const request) {
        /* some stuff here */

        callback(*request);
    });
}

// OPTION C: forward callback to function + move to lambda
void registerRoute(
    const char* const uri,
    const HttpMethod method,
    std::function<void(Request& request)>&& callback
) {
    server.on(uri, method, [&, callback = std::move(callback)] (Request* const request) {
        /* some stuff here */

        callback(*request);
    });
}

// ~~OPTION D~~: reference callback to function, reference/move to lambda
//           => does NOT work -> as the passed–in callback has to outlive registerRoute function

// OPTION E: copy callback to function, copy to lambda
//           => works, but is wasteful I guess ;-) IDE suggests to move or reference.