/*
 * Creator_impl.hpp
 *
 *  Created on: Jan 3, 2011
 *      Author: heber
 */

#ifndef CREATOR_IMPL_HPP_
#define CREATOR_IMPL_HPP_

// include config.h
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif


/** This class wraps another one and implements a create() function for it.
 *
 * This pattern is sometimes called 'type erasure': we want to present
 * the user with a abstract interface only (name) but in
 * order to create a copy (such that handed out instances are independent from
 * one another) we have to know about the type of underlying (complex) class.
 *
 * Hence, we create this templated creator class (name##_Creator), which has an
 * abstract creation interface (I##name##_Creator).
 *
 * This pattern is e.g. very useful when multiple (proto)types have to be
 * stored in the table of a factory. Factories can serve only a general
 * (abstract) type and not the specific one due to a necessary general function
 * signature.
 *
 * <h1> Howto </h1>
 *
 * Wrap the classes to instantiate by the factory in this creator
 * pattern. The factory in its tables only stores the abstract creation
 * interface (I##name##_Creator). Let the factory call create() when it has to
 * produce an instance, which is passed through to the templated creation class
 * (name##_Creator), dealing out the copy.
 *
 * <h1>Best Practice </h1>
 *
 * NOTE: It is best-practice to place the call to CONSTRUCT_CREATOR in its
 * own header file and include this file only. Otherwise, one might get
 * redefinition errors.
 */
#define CONSTRUCT_CREATOR(name) \
class name; \
struct I##name##_Creator \
{ \
  virtual ~I##name##_Creator() {}; \
  virtual  name * create() const =0; \
}; \
template <class T> \
struct name##_Creator : public I##name##_Creator \
{ \
  virtual name * create() const { \
    return new T(); \
  }; \
};


#endif /* CREATOR_IMPL_HPP_ */