简单模板单例

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <iostream>
using namespace std;

#define BT_SAFE_DELETE(p)       if ((p)) {delete (p);(p) = NULL;}

/*
 * 这里没有考虑多线程会new出不同对象的问题，并不是严格意义上的单例
 */
template<class T>///T类型
class singleton
{
public:
    inline static T* instance();
    inline static void uninstance();
protected:        
    static void _new_instance();
    static void _delete_instance();

private:
    static T* _instance;
};

template<class T>
T* singleton<T>::_instance = NULL;

template<class T>
inline T* singleton<T>::instance()
{
    if (_instance == NULL)
    {
        _new_instance();
    }
    return _instance;
}

template<class T>
inline void singleton<T>::uninstance()
{
    _delete_instance();
}

template<class T>
void singleton<T>::_new_instance()
{
    if (_instance == NULL)
    {
        T* tmp = new T;
        _instance = tmp;
    }
}

template<class T>
void singleton<T>::_delete_instance()
{
    BT_SAFE_DELETE(_instance);
}

class A:public singleton<A>
{
public:
    A()
    {
        cout << "construct class A" << endl;
    }

    ~A()
    {
        cout << "destory class A" << endl;
    }

    void f()
    {
        cout << "function f" << endl;
    }
};

int main()
{
    {
        A::instance()->f();
        A::uninstance();
    }

    return 0;
}