singleton.hpp

"More for C++" is a class library that provides some features that are usually common for object ori

//
//  This file is part of the "More for C++" library
//
//  Copyright (c) 1999-2003 by Thorsten Goertz ([e-mail])
//
//  The "More for C++" library is free software; you can redistribute it and/or
//  modify it under the terms of the license that comes with this package.
//
//  Read "license.txt" for more details.
//
//  THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED
//  WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES
//  OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.

////////////////////////////////////////////////////////////////////////////////

#ifndef MORE_UTIL_SINGLETON_HPP
#define MORE_UTIL_SINGLETON_HPP

//////////////////////////////////////////////////////////////////////////

#include <more/pointer.hpp>

////////////////////////////////////////////////////////////////////////////////

namespace more
{
  namespace util
  {
    class SingletonBase
    {
      protected:
        static p<SingletonBase> access( SingletonBase*& rpInstance,
                                        SingletonBase*  pNewInstance,
                                        bool            bUpdateInstance );
        virtual ~SingletonBase( );
    };

    template<typename Type>
    class Singleton: public SingletonBase
    {
      public:
        static p<Type> getInstance( );

      protected:
        static void setInstance( const p<Type>& );

      private:
        static p<Type> access( Type* pNewInstance, bool bUpdateInstance );
    };
  }
}

////////////////////////////////////////////////////////////////////////////////

template<typename Type>
inline more::p<Type> more::util::Singleton<Type>::getInstance( )
{
  return Singleton<Type>::access( 0, false );
}

////////////////////////////////////////////////////////////////////////////////

template<typename Type>
inline void more::util::Singleton<Type>::setInstance
(
  const p<Type>& pNewInstance
)
{
  Singleton<Type>::access( pNewInstance, true );
}

////////////////////////////////////////////////////////////////////////////////

template<typename Type>
inline more::p<Type> more::util::Singleton<Type>::access
(
  Type* pNewInstance,
  bool  bUpdateInstance
)
{
  static SingletonBase* pInstance = 0;

  p<SingletonBase> pResult = SingletonBase::access( pInstance,
                                                    pNewInstance,
                                                    bUpdateInstance );

  return pResult == 0 ? 0 : cast<Type>( pResult );
}

////////////////////////////////////////////////////////////////////////////////

#endif