C++ Factory Pattern With Templates

Question

I'm trying to code an abstract factory using c++ templates. Due to the fact I've never done things like that before I'm encountering troubles. The code I wrote, as you can verify by yourself, is wrong and I have no idea on how to correct it. My idea is that there are two templated classes that will contain the base_class and the derived_class, so this class can be used with any type of class. It is templated the key too for the same reason.

#ifndef _t_factory_h_
#define _t_factory_h_

#include <iostream>
#include <map>

template < class T >
class base_creator
{
  public:
   virtual ~base_creator(){ };
   virtual T* create() = 0;
};


template < class derived_type , class base_type >
class derived_creator : public base_creator<base_type>
{
  public:
  base_type* create()
  {
   return new derived_type;
  }
};

template <class _key, class base >
class factory
{
   public:
     void register_type(_key id , derived_creator<derived_type,base_type>* _fn)
  {
    _function_map[id] = _fn;
  }

  base* create(_key id)
  {
    return _function_map[id]->create();
  }

 ~factory()
 {
   auto it = _function_map.begin();
   for(it ; it != _function_map.end() ; ++it)
   {
     delete (*it).second;
   }
  }

  private:
     std::map<_key , derived_creator<derived_type,base_type>*> _function_map;
   };

#endif /* defined _t_factory_h_ */

If somenone can help me to correct this code I would be grateful.

Answer 1

Problem solved. Here is the code:

#ifndef _t_factory_h_
#define _t_factory_h_

#include <iostream>
#include <map>

template < class T >
class base_creator
{ 
  public:
  virtual ~base_creator(){ };
  virtual T* create() = 0;
};


template < class derived_type , class base_type >
class derived_creator : public base_creator<base_type>  
{
 public:
 base_type* create()
 {
  return new derived_type;
 }
};

template <class _key, class base_type >
class factory
{
 public:
   void register_type(_key id , base_creator<base_type>* _fn)
   {
     _function_map[id] = _fn;
   }

   base_type* create(_key id)
   {
      return _function_map[id]->create();
   }

  ~factory()
  {
    auto it = _function_map.begin();
    for(it ; it != _function_map.end() ; ++it)
    {
      delete (*it).second;
    }
}

 private:
   std::map<_key , base_creator<base_type>*> _function_map;
};

#endif /* defined _t_factory_h_ */