singleton.h

特别好玩有启发的东西

/***************************************************************
*Copyright (c) 金瀚海网络科技有限公司 All rights reserved
*文件名称: define.h
*模 块 名: 定义文件
*功能描述: 全局常量符号定义
*当前版本: 1.0
*作    者: 彭飞云
*完成日期: 2007-08-20
*修改记录: 
*  日期			版本    作者        修改描述
****************************************************************

****************************************************************/

#ifndef SINGLETON_H
#define SINGLETON_H

#include <stdexcept>

#define DEBUG_SINGLETON


#ifdef DEBUG_SINGLETON
#define TEST_STRING(sentence) printf(sentence);
#else 
#define TEST_STRING(sentence) 
#endif



using namespace std;


template<class SubClass>
class Singleton
{
private:
	static SubClass* _instance;
	static bool	_create_by_instance;
public:
	static	SubClass * Instance();
protected:
	Singleton() 
	{
		if(!_create_by_instance)
			throw std::runtime_error ("can't create object by subclass");
	}
};


template<class SubClass>
SubClass * Singleton<SubClass>::Instance ()
{
	if(false == _create_by_instance){
		if(_instance == NULL){
			_create_by_instance = true;
			try{
				_instance = new SubClass();
			}
			catch(...){
				_instance = 0;
				_create_by_instance = false;//
				throw;
			}
			//_create_by_instance = true;
			return _instance;
		}else{
			TEST_STRING("Singleton class error!\n")
			return NULL;
		}
	}else{//_create_by_instance == true;
		if(_instance == NULL)
			TEST_STRING("Singleton class error!\n")
		return _instance;
	}

/*
	if( _instance == 0 )
	{
		_create_by_instance = true;
		//
		try
		{
			_instance = new SubClass();
		}
		catch(...)
		{
			_create_by_instance = false;//	
			throw;
		}
		_create_by_instance = false;//
	}
*/
//	return _instance;
}


template<class SubClass>
SubClass * Singleton<SubClass>::_instance = 0;

template<class SubClass>
bool Singleton<SubClass>::_create_by_instance = 0;

#endif //SINGELTON_H