设计模式 - 单件模式 C++

#ifndef _SINGLETON_H_
#define _SINGLETON_H_

class singleton
{
private:
static singleton _instance;

int _i;

singleton(int i) : _i(i) {};

singleton& operator = (singleton&);

singleton(const singleton&);

public:
static singleton& instance();

int getvalue();

void setvalue(int i);

};

#endif

#include "singleton.h"

singleton singleton::_instance(0);

int singleton::getvalue()
{
return _i;
}

void singleton::setvalue(int i)
{
_i = i;
}

singleton& singleton::instance()
{
return _instance;
}

#include <iostream>
#include "singleton.h"

using namespace std;

void main()
{
int i = 0;

singleton &s1 = singleton::instance();

cout << s1.getvalue() << endl;

s1.setvalue(20);

cout << s1.getvalue() << endl;

cin >> i;
}