How to implement the factory method pattern in C++ correctly

Question

There\'s this one thing in C++ which has been making me feel uncomfortable for quite a long time, because I honestly don\'t know how to do it, even though it sounds simple:<

Answer 1

extern std::pair const factories[2];

decltype(factories) factories{
  {"blah", []() -> Base*{return new Blah;}},
  {"foo", []() -> Base*{return new Foo;}}
};