Dynamic Class Factory

// ******************************************************************************
// *
// * Copyright (c) 2003,2004 by Mirec Miskufovic (mirec(dot)m(at)gmx(dot)com).
// * All rights reserved.
// * Permission to use and modify (commercial or non-commercial) is hereby granted subject to inclusion of this copyright notice.
// *
// * It is not allowed to republish the source code so that it is accessible to the public without first obtaining the copyright owner's permission.
// *
// ******************************************************************************
//
// Title        : ClassFactory.h
// Description  : interface for the CClassFactory class
// Created      : 19/08/2003 16:46:18
// Author       : M.Miskufovic
//
// ------------------------------------------------------------------------
// ------------------------------------------------------------------------

#if !defined(AFX_CLASSFACTORY_H__CA6330BC_AF6C_460C_AED0_0E76E9D96D55__INCLUDED_)
#define AFX_CLASSFACTORY_H__CA6330BC_AF6C_460C_AED0_0E76E9D96D55__INCLUDED_

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000

#include <map>

template <typename _Key, typename _Base, typename _Predicator = std::less<_Key> >
class CClassFactory
{
public:
	CClassFactory() {};
	~CClassFactory() {};

	typedef _Base* (*CreatorFunction) (void);
	typedef std::map<_Key, CreatorFunction, _Predicator> _mapFactory;

	// called at the beginning of execution to register creation functions
	static _Key RegisterCreatorFunction(_Key idKey, CreatorFunction classCreator)
	{
		get_mapFactory()->insert(std::pair<_Key, CreatorFunction>(idKey, classCreator));
		return idKey;
	}

	// Tries to create instance based on the key
	// using creator function (if provided)
	static _Base* CreateInstance(_Key idKey)
	{
		_mapFactory::iterator it = get_mapFactory()->find(idKey);
		if (it != get_mapFactory()->end())
		{
			if (it->second)
			{
				return it->second();
			}
		}
		return NULL;
	}

protected:
	// Map where the construction info is stored.
	// To prevent inserting into map before initialisation takes place,
	// actual map is a static member, so it will be initialised
	// at the first call
	static _mapFactory * get_mapFactory()
	{
		static _mapFactory m_sMapFactory;
		return &m_sMapFactory;
	}
};

#endif // !defined(AFX_CLASSFACTORY_H__CA6330BC_AF6C_460C_AED0_0E76E9D96D55__INCLUDED_)