c++ - How to set up a std container with a RAII class? -


to realize idiom type socket, have created wrapper. wrapper calls connect in constructor , closesocket in destructor. std::map holds used sockets. unfortunatelly inserting new socket container calls destructor of temporary and, in fact, closes opened socket. there common way overcome this?

here code:

#include <iostream> #include <stdexcept> #include <map> #include <winsock2.h>  struct socket {     socket msock;     socket() : msock(invalid_socket) {}     socket(std::string ip, int port);     ~socket(); };  socket::socket(std::string ip, int port) {     msock = socket(af_inet, sock_stream, 0);     if (msock == invalid_socket)         throw std::runtime_error("socket()");     sockaddr_in addr = {0};     addr.sin_family = af_inet;     addr.sin_port = htons(port);     addr.sin_addr.s_addr = inet_addr(ip.c_str());     if (connect(msock, reinterpret_cast<sockaddr*>(&addr), sizeof(addr))         == socket_error)         throw std::runtime_error("connect()");     std::cout << msock << " connected" << std::endl; }  socket::~socket() {     if (msock != invalid_socket) {         closesocket(msock);         std::cout << msock << " closed" << std::endl;     } }  int main() {     wsadata wsa;     wsastartup(makeword(2, 0), &wsa);     std::map<int, socket> outbound;     // calls constructur destructor     outbound[0] = socket("192.168.128.125", 4023);     wsacleanup();     return 0; }

and output is:

1952 connected 1952 closed 1952 closed

resource guards may stored in stl containers if wrap them in smart pointer. smart pointer use environment, i'd recommend go boost::shared_ptr starting point if you're not sure.

following way conform both resource guard semantics (only 1 instance manages resource's lifetime) , stl container (keep equivalent copy of passed item).


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