设计模式之 单例模式

#include <iostream>
#include <string>
using std::cout;
using std::cin;
using std::endl;
using std::string;

/*
template<class T,  class StaticMutex>
class SingleInstance
{
protected:
SingleInstance(void){}
virtual ~SingleInstance(void){}
T* CreateInstance(void)
{
if(!pIns_)
{
mutex_.lock();
if(!pIns_)
{
pIns_ = new T();
}
mutex_.unlock();
}
return pIns_;
}
void destoryInstance()
{
if(pIns_)
{
delete pIns_;
pIns_ = NULL;
}
}
private:
static T *pIns_;
StaticMutex mutex_;
};
*/

template<class T>
class SingleInstance
{
protected:
SingleInstance(void){}
virtual ~SingleInstance(void){}
static T* createInstance(void)
{
if(!pIns_)
{
pIns_ = new T();
}
return pIns_;
}
void destoryInstance()
{
if(pIns_)
{
delete pIns_;
pIns_ = NULL;
}
}
private:
static T *pIns_;
};

template<typename T>
T* SingleInstance<T>::pIns_ = NULL;

class Factory: public SingleInstance<Factory>
{
public:
Factory(void){}
~Factory(void){ destoryInstance(); }
static Factory* instance(void){ return createInstance(); }

void show(){ cout<<"create a factory instance ok"<<endl; }
};

int main()
{
Factory::instance()->show();
return 0;
}