设计模式之单例模式

此单例模式非内存泄漏非线程安全。

singleton.h

#pragma once#define DISALLOW_COPY(TypeName) \    TypeName(const TypeName&){}#define DISALLOW_ASSIGN(TypeName) \    TypeName operator=(const TypeName&){}#define DISALLOW_COPY_AND_ASSIGN(TypeName) \    TypeName(const TypeName&) {} \    TypeName operator=(const TypeName&){}#include <memory>#include <iostream>using namespace std;class Singleton{public:    ~Singleton();private:    explicit Singleton();    DISALLOW_COPY_AND_ASSIGN(Singleton)public:    static Singleton *getInstance();private:    static Singleton *m_pInstance;//    static std::shared_ptr<Singleton> m_pInstance;//private://    class Deleter//    {//    public://        Deleter()//        {//            cout << "Deleter()" << endl;//        }//        ~Deleter()//        {//            cout << "~Deleter()" << endl;//            if (NULL != Singleton::m_pInstance)//            {//                delete Singleton::m_pInstance;//            }//        }//    };//    // 定义一个静态的Deleter实例//    static Deleter deleter;};

singleton.cpp

#include "Singleton.h"Singleton *Singleton::m_pInstance;//std::shared_ptr<Singleton> Singleton::m_pInstance;//Singleton::Deleter Singleton::deleter;Singleton::~Singleton(){    cout << "~Singleton()" << endl;}Singleton::Singleton(){    cout << "Singleton()" << endl;}Singleton *Singleton::getInstance(){//    //懒汉模式（会内存泄漏, 如果类内部定义静态Deleter实例也不会内存泄露）//    if (NULL == m_pInstance)//        m_pInstance = new Singleton();//    return m_pInstance;    //饿汉模式（不会内存泄露）    static Singleton instance;    return &instance;//    //懒汉模式（采用智能指针，不会内存泄漏）//    if (nullptr == m_pInstance.get())//    {//        m_pInstance = std::auto_ptr<Singleton>(new Singleton);//    }//    return m_pInstance.get();}

切记一点：Qt项目中，单例模式主动delete窗体会和Qt本身对象树析构机制冲突，造成二次析构，从而导致出现无法访问0xfffffffe之类的错误，Qt析构机制只是将对象delete掉，并不会将对象置为NULL。