C / C++ / MFC

TypeA myType;
myType = WIN;

XYZ<MyClass, myType> zyx;

// A.h
class A
{
  typedef A* (creator *)();
  typedef map<int,creator> creators_map;
  static creators_map m;
protected:
  static void register(int n,creator c)
  {
    m[n]=c;
  }
public:
  A* create(int n)
  {
    creators_map::iterator it=m.find(n);
    if(it==m.end())return 0;
    return it->second();
  }
  //virtual member functions go here
};
// A1.h
class A1: public A
{
  static A* create(){return new A1;}
public:
  static void register() //this has to be explicity called somewhere
  {
    A::register(1,create);
  }
  ...
};