错误：调用'uWS::TemplatedApp<false>::ws<main()::UserData>(const char [3], <brace-enclosed

Question

我正在使用uwebsockets来创建ws服务器。

main.cpp：

int main()
{
struct UserData {
};
uWS::App().ws<UserData>("/*", {
/* Just a few of the available handlers */
.open = [](auto *ws) {
/* MQTT syntax */
ws->subscribe("sensors/+/house");
},
.message = [](auto *ws, std::string_view message, uWS::OpCode opCode) {
ws->send(message, opCode);
}
}).listen(9001, [](auto *listenSocket) {
if (listenSocket) {
std::cout << "Listening on port " << 9001 << std::endl;
}
}).run();
return 0;
}

构建时的错误消息：

……main.cpp:22:4: note:   cannot convert '{<lambda closure object>main()::<lambda(auto:11*)>{}, <lambda closure object>main()::<lambda(auto:12*, std::string_view, uWS::OpCode)>{}}' (type '<brace-enclosed initializer list>') to type 'uWS::TemplatedApp<false>::WebSocketBehavior<main()::UserData>&&'
}).listen(9001, [](auto *listenSocket) {
^

环境：

操作系统：Windows10 64位

IDE:QtCreator

编译器：MinGW 8.1.0 32位

c++标准：17

uwebsockets:19.2.0

Answer 1

这是因为编译器无法将'brace enclosed initializer list'转换为T&amp；。它可以通过声明结构并将其转换为Rvalue引用来解决。

struct UserData {
};
uWS::TemplatedApp<false>::WebSocketBehavior<UserData> wsb = {
/* Just a few of the available handlers */
.open = [](auto *ws) {
/* MQTT syntax */
ws->subscribe("sensors/+/house");
},
.message = [](auto *ws, std::string_view message, uWS::OpCode opCode) {
ws->send(message, opCode);
}
};
uWS::App().ws<UserData>("/*", std::move(wsb)).listen(9001, [](auto *listenSocket) {
if (listenSocket) {
std::cout << "Listening on port " << 9001 << std::endl;
}
}).run();