emplacing object with variadic constructor into map

Question

I have a movable (but not copyable) type with a variadic template constructor

struct foo
{
  std::string a,b,c;
  foo(foo const&)=delete;
  foo(foo&&)=default;
  template<typename...T>
  for(T&&...);
};

and I want to add it into a map:

template<typename...T>
void add_foo(std::map<std::string,foo>&map, const char*name, T&&...args)
{
  map.emplace(std::piecewise_construct,      // how? perhaps like this?
              std::forward_as_tuple(name),   //   no:
              std::forward_as_tuple(args));  //   error here
}

Answer 1

std::forward_as_tuple() takes a pack, so you can simply expand args using ...:

map.emplace(std::piecewise_construct,
            std::forward_as_tuple(name),
            std::forward_as_tuple(args...));

Answer 2

You need to unpack the arguments: args...

See it Live On Coliru

#include <string>
#include <map>

struct foo
{
    std::string a,b,c;
    foo(foo const&)=delete;
    foo(foo&&)=default;
    template<typename...T> foo(T&&...) {}
};


template<typename...T>
void add_foo(std::map<std::string,foo>& map, const char*name, T&&...args)
{
    map.emplace(std::piecewise_construct,      // how? perhaps like this?
            std::forward_as_tuple(name),   //   no:
            std::forward_as_tuple(args...));  //   error here
}

int main()
{
    std::map<std::string,foo> m;
    add_foo(m, "a", "b", "c");
}