c++ 实现多线程安全的单例模板类

单类模板代码:

#pragma once
#include <QMutex>

template <class T>
class Singleton
{
protected:
    Singleton(){};
    
private:
    Singleton(const Singleton&){};
    Singleton& operator=(const Singleton&){};
    static T* m_instance;
    static QMutex m_mutex;
public:
    static T* GetInstance();
};

template <class T>
T* Singleton<T>::GetInstance()
{
    if( m_instance == NULL)
       {
           m_mutex.lock();
           if( m_instance == NULL)
           {
                T* ptmp = new T();
                m_instance = ptmp;
           }
           m_mutex.unlock();
       }
       return m_instance;
}

template <class T>
T* Singleton<T>::m_instance = NULL;
#endif // Singleton_H

 

使用单类模板

#include <iostream>
#include <string>
#include "Singleton.h"

using namespace std;

class Test
{
       friend class Singleton<Test> ;  //声明Test的友元为单例类模板
private:   
       string mstr;

        Test(): mstr("abc")
       {
       }

       Test& operator = (const Test& t);
       Test(const Test&);

public:    
        void Setmstr(string t)
　　　　{
         mstr=t;
　　　　}

        void print()
       {
        cout<<"mstr = "<<mstr<<endl;
        cout<<"this = "<<this<<endl;
       }
};

int main()
{
        Test *pt1 = Singleton<Test>::getInstance();
        Test *pt2 = Singleton<Test>::getInstance();   

        pt1->print();
        pt2->print();

        pt1->Setmstr("ABCDEFG");
        pt2->print();

        return 0;
}