用模板和智能指针实现单件模式

#ifndef SINGLETON_H
#define SINGLETON_H

#include <boost/smart_ptr.hpp>

template< class T >
class singleton
{
public:
    typedef boost::shared_ptr< T > T_sptr;

    static T_sptr instance()
    {
        static T_sptr _instance;
        if (_instance.get() == 0)
        {
            _instance.reset(new T);
        }
        return _instance;
    }
protected:
    singleton()
    {
    }
};

#endif // SINGLETON_H