C++11 trick to create some classes by their ID names.

gistfile1.cpp

#include <string>
#include <map>
#include <iostream>
#include <utility>
#include <functional>

struct Interface {
  virtual void method() = 0; // May be a visitor pattern
};

template <class T> Interface* InterfaceBuilder(void) { return new T(); };

class Factory {
  using interface_builder_func_type = std::function<Interface*(void)>;
  std::map<std::string, interface_builder_func_type> classes_;
  static Factory * instance_;

  Factory();
 public:
  static std::string RegisterID(std::string const & id, interface_builder_func_type builder);
  static Factory& getInstance();
  Interface * newInstance(std::string const & id);
};

Factory* Factory::instance_ = nullptr;

Factory::Factory(){}

Interface * Factory::newInstance(std::string const & id) {
  Interface * instance = nullptr;
  std::map<std::string, interface_builder_func_type>::const_iterator func_iter = classes_.find(id);
  if(func_iter != classes_.end()){
    instance = (func_iter->second)();
  }
  return instance;
}

std::string Factory::RegisterID(std::string const & id, interface_builder_func_type builder) {
  Factory & factory = getInstance();
  factory.classes_.insert(std::make_pair(id, builder));
  return id;
}

Factory& Factory::getInstance() {
  if(!instance_) {
    instance_ = new Factory();
  }
  return *instance_;
}

// Here the real shit begins
class MessageStart : public Interface {
 public:
  MessageStart();
  static std::string const ClassId;
  virtual void method();
};

std::string const MessageStart::ClassId = Factory::RegisterID("ID1", InterfaceBuilder<MessageStart>);

MessageStart::MessageStart() {}

void MessageStart::method() {
  std::cout << "I am a start message !" << std::endl;
}

class MessageStop : public Interface {
 public:
  MessageStop();
  static std::string const ClassId;
  virtual void method();
};

std::string const MessageStop::ClassId = Factory::RegisterID("ID2", InterfaceBuilder<MessageStop>);

MessageStop::MessageStop() {}

void MessageStop::method() {
  std::cout << "I am an end message !" << std::endl;
}

// Demo
int main() {
  Factory & factory = Factory::getInstance();

  Interface * msg_start = factory.newInstance("ID1");
  msg_start->method();
  delete msg_start;

  Interface * msg_stop = factory.newInstance("ID2");
  msg_stop->method();
  delete msg_stop;
  return 0;
}