设计模式-单例模式

使用情境:确保一个类仅有一个对象实例.

// singleton.h
#ifndef SINGLETON_H
#define SINGLETON_H

class Singleton
{
private:
    Singleton();
    static Singleton* single_instance;
public:
    static Singleton* GetInstance();
};

#endif // SINGLETON_H

// singleton.cpp
#include "singleton.h"
#include <stdlib.h>

Singleton* Singleton::single_instance = NULL;

Singleton::Singleton(){}

Singleton* Singleton::GetInstance()
{
    if(single_instance == NULL)
    {
        single_instance = new Singleton();
    }
    return single_instance;
}

客户端:

// main.cpp
#include <iostream>
#include "singleton.h"

using namespace std;

int main(int argc, char *argv[])
{
    Singleton* s1 = Singleton::GetInstance();
    Singleton* s2 = Singleton::GetInstance();
    if(s1 == s2)
        cout << "same" << endl;
    else
        cout << "diff" << endl;
    return 0;
}