c++ - 将具有可变参数构造函数的对象放置到 map 中

Question

我有一个带有可变模板构造函数的可 move (但不可复制)类型

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

我想将它添加到 map 中:

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() 需要一个包，因此您可以使用 ... 简单地扩展 args:

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