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/home/pauldt/projects/IDEA/IDEA-ALL/IDEA-DEV/Core/Utilities/Includes/Factory.hh

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// -*- Mode: c++ -*-
//     File: $Source: /home/cvs/ISG-Repository/IDEA-DEV/Core/Utilities/Includes/Factory.hh,v $
//      Tag: $Name: DR_01_11_06 $
//      CVS: $Id: Factory.hh,v 1.3 2005/12/30 22:06:24 rijsman Exp $
//     Info: $CVSROOT/IDEA-DEV/COPYRIGHT

#ifndef FACTORY_HEADER_DEFINITION
#define FACTORY_HEADER_DEFINITION

#include "Debugging.hh"
#include "Trace.hh"
#include "Utilities.hh"

namespace IDEA
{
  template< class Type >
  class Factory
  {
  private:
    typedef std::map< std::string, const Factory* > String2Type;
  public:
    Factory( const std::string& key ):
      m_Key( key )
    {
      registerFactory( this );
    }
    virtual ~Factory() 
    {
      unRegisterFactory( this );
    }
    const std::string& getKey() const
    {
      return m_Key;
    }
    static void useKey( const std::string& key )
    {
      // this will work, looks a little weird but see comments at getUseKey
      getUseKey() = key;
    }
    static const Type* instance() 
    {
      typename String2Type::const_iterator ite = getContainer().find( getUseKey() );

      if( ite != getContainer().end() )
        {
          ASSERT( 0 != dynamic_cast< const Type* >(ite->second) );

          // HERE we make a strong ASSUMPTION Type is a specialization of Factory
          return static_cast<const Type*>(ite->second);
        }
      else
        {
          ERROR_MSG("Requested to use factory instance '"
                    << getUseKey() << "' but no such instance has been registered for type '"
                    << typeid( Type ).name() << "'. Did you load the library which registers this factory?");
        }

      return 0;
    }
  private:
    Factory();
    Factory( const Factory& factory );
    static std::string& getUseKey()
    {
      static std::string useKey = "";

      return useKey;
    }
    static String2Type& getContainer() 
    {
      static String2Type* container = new String2Type();

      return *container;
    }
    static void registerFactory( const Factory* factory )
    {
      getContainer().insert( std::make_pair( factory->getKey(), factory ) );
    }
    static void unRegisterFactory( const Factory* factory )
    {
      typename String2Type::iterator ite = getContainer().find( factory->getKey() );

      if( ite != getContainer().end() )
        getContainer().erase( ite );
    }
    std::string m_Key;
  };
}

#endif // FACTORY_HEADER_DEFINITION

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