【设计模式】Singleton Pattern

#include "Singleton.h"
#include <iostream>
using namespace std;

int main(int argc, char *argv[]) {
    
    Singleton *sgn = Singleton::Instance();

    return 0;
}

#ifndef _SINGLETON_H
#define _SINGLETON_H

class Singleton {
public :
    static Singleton *Instance();
protected :
    Singleton();
private :
    static Singleton *_instance;
};

#endif

#include "Singleton.h"
#include <iostream>
using namespace std;

Singleton *Singleton::_instance = 0;

Singleton::Singleton() {
    cout << "Singleton..." << endl;
}

Singleton *Singleton::Instance() {

    if (_instance == 0) {
        _instance = new Singleton();
    }

    return _instance;
}