C++单例模式实现

C++单例模式实现

test.h

#pragma once
class CSingleInstance
{
public:
	static CSingleInstance* GetInstance();
private:
	CSingleInstance();
	CSingleInstance(CSingleInstance& ss){};
	CSingleInstance& operator=(CSingleInstance& ss){};
	~CSingleInstance();
	static CSingleInstance* pInstance;//仅仅申明未定义

};

test.cpp

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

CSingleInstance* CSingleInstance::pInstance = NULL;


CSingleInstance* CSingleInstance::GetInstance()
{
	if (!pInstance)pInstance = new CSingleInstance;
	return pInstance;
}

CSingleInstance::CSingleInstance() {
	std::cout << "instance create" << std::endl;
}

CSingleInstance::~CSingleInstance() {
	std::cout << "instance destory" << std::endl;
}

main.cpp

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

int main()
{
	CSingleInstance* a = CSingleInstance::GetInstance();
	CSingleInstance* b = CSingleInstance::GetInstance();
	cout << a << endl;
	cout<< b <<endl;
}

执行结果
instance create
013CB5D0
013CB5D0

可以看到析构函数并未被调用

解决：

test.h

#pragma once
class CSingleInstance
{
public:
	static CSingleInstance* GetInstance();
private:
	CSingleInstance();
	CSingleInstance(CSingleInstance& ss){};
	CSingleInstance& operator=(CSingleInstance& ss){};
	~CSingleInstance();
	static CSingleInstance* pInstance;//仅仅申明未定义

	class CHelper {
	public:
		CHelper();
		~CHelper();
	};
	static CHelper helper;//未定义
};

test.cpp

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

CSingleInstance* CSingleInstance::pInstance = NULL;

CSingleInstance::CHelper CSingleInstance::helper;

CSingleInstance* CSingleInstance::GetInstance()
{
	if (!pInstance)pInstance = new CSingleInstance;
	return pInstance;
}

CSingleInstance::CSingleInstance() {
	std::cout << "instance create" << std::endl;
}

CSingleInstance::~CSingleInstance() {
	std::cout << "instance destory" << std::endl;
}

CSingleInstance::CHelper::CHelper()
{
	GetInstance();
}

CSingleInstance::CHelper::~CHelper()
{
	if (pInstance) {
		CSingleInstance* tmp = pInstance;
		pInstance = NULL;
		delete tmp;
	}
}