C? ??? ?? ????? ??? ?????? ? ?????

C?? ??? ??? ???? ????? ??? ??????? ????? ????? , ????? ????? ??? ? ???? ?? if-else ?? ????? ??? ??? ????. ????

??:

?? ??? ??? ?????.

class Base;
class DerivedA : public Base;
class DerivedB : public Base;
// etc...

??? ?? ??? ???? BaseFactory? ?? ???? ????? ?????. ??? ??? ?? ???? ???? ?? ???:

class BaseFactory {
public:
  BaseFactory(std::string &sClassName) { msClassName = sClassName; };

  Base * Create() {
    if(msClassName == "DerivedA") {
      return new DerivedA();
    }
    else if(msClassName == "DerivedB") {
      return new DerivedB();
    }
    // etc...
  };

private:
  string msClassName;
};

??? ? ?? ???? ???? ?? ??? ?????. BaseFactory ??? ? ?? ???? ???? ?? ?? ??? ?? ???? ?? ???? ? ????.

???:

C#? ?? ??? ?? C? ????? ??? ???? ????. ??? ?? ??? ???? ??? ???? ???? ???????. ??? ??? ????? ??? ??? ?? ?? ?? ?? ?? ??? ??? ? ????.

template<typename T> Base * createInstance() { return new T; }

typedef std::map<std::string, Base*(*)()> map_type;

map_type map;
map["DerivedA"] = &createInstance<DerivedA>;
map["DerivedB"] = &createInstance<DerivedB>;

? ?? ???? ?? ?????? ??? ?? ???.

return map[some_string]();

?? ??? ?? ??? ? ????. ???? ??? ?? ???? ?? ???:

template<typename T>
struct DerivedRegister : BaseFactory { 
    DerivedRegister(std::string const& s) { 
        getMap()->insert(std::make_pair(s, &createT<T>));
    }
};

// in derivedb.hpp
class DerivedB {
    ...;
private:
    static DerivedRegister<DerivedB> reg;
};

// in derivedb.cpp:
DerivedRegister<DerivedB> DerivedB::reg("DerivedB");

? ?? ??? ???? ???? ????? ?? ??? ??? ???? ????.

??:

C? ??? ?? ????? ?? ?????? ?? ???? ??? ??? ??? ??? ?? ??? ??? ???? ??? ?????. ??? ??? ?? ?? ??? ????? ?? ????? ??????.

? ??? C? ??? ?? ????? ??? ?????? ? ?????? ?? ?????. ??? ??? PHP ??? ????? ?? ?? ??? ?????!