if I have this map
std::unordered_map<std::string, int*> sockets; //a map holding all active sockets how come I can do this :
sockets[_myId]=(int*)lp; //all ok - insert succeeds but I can't do this :
if(!sockets.emplace(_myId,(int*)lp).second) { /*insert failed, act accordingly*/ } Invalid arguments ' Candidates are: ? emplace(#10000(...) && ...) ' I don't understand why this happens. Thx for any assistance.
What's a better way to write it then?
This is an unordered map mapping some identifier with a number of sockets.
In BSD sockets, a socket descriptor is an int (or at least convertible to one) so lets stay with that.
It seems that there are more than one socket associated with each identifier. This argues for a vector.
so:
using socket_vector = std::vector<int>; and
using ident_to_sockets = std::unordered_map<std::string, socket_vector>; now we can append sockets to each ident:
sockets[ident].push_back(sock); 
std::unordered_map<std::string, int*> something; std::string a; int* b; something[a] = b; // with emplace: something.emplace(std::make_pair(a, b)); // also something.emplace(std::unordered_map<std::string, int*>::value_type(a, b)); 
std::unordered_map<std::string, int*> sockets; bool foo(const char *p, int n) { return sockets.emplace(p, &n).second; }