问题描述
我正在使用 uwebsockets 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 32bit
c++std:17
uwebsockets: 19.2.0
解决方法
这是因为编译器无法将“大括号括起来的初始化列表”转换为 T&&。可以通过声明结构体并将其转换为右值引用来解决。
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();