稍微有点感冒，鼻子就难受的不行,都怪那个倒霉的周二没有把头发吹干。不过还是把这几行代码写完吧。。。 。。。

今天来看看备忘录模式.

UML图很简单：

代码也不是很复杂，下面是C++实现

/*
 * Copyright (c) 2017 initm.com All rights reserved.
 * 作者: Stupid
 * 描述: 备忘录模式
 * 完成时间: 2017-11-2 20:37
*/

#include <QCoreApplication>
#include <iostream>
#include <string>

//备忘录类
class Memento
{
private:
    std::string state;

public:
    Memento(const std::string& state): state(state){
    }
    std::string GetState(){
        return state;
    }
};

//发起人类
class Originator
{
private:
    std::string state;

public:
    std::string GetState(){
        return state;
    }
    void SetState(const std::string& state){
        this->state = state;
    }
    Memento* CreateMemento(){
        return new Memento(state);
    }
    void SetMemento(Memento* memento){
        if(nullptr == memento){
            return ;
        }
        state = memento->GetState();
    }
    void Show(){
        std::cout << "State=" << state << std::endl;
    }
};

//管理者类
class Caretaker
{
private:
    Memento* memento = nullptr;

public:
    Memento* GetMemento(){
        return memento;
    }
    void SetMemento(Memento* memento){
        if(nullptr != this->memento){
            delete this->memento;
        }
        this->memento = memento;
    }
};

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    Originator* originator = new Originator;
    originator->SetState("on");
    originator->Show();

    Caretaker* caretaker = new Caretaker;
    caretaker->SetMemento(originator->CreateMemento());

    originator->SetState("off");
    originator->Show();

    originator->SetMemento(caretaker->GetMemento());
    originator->Show();

    delete caretaker;
    delete originator;

    return a.exec();
}

通过创建一个备忘录，我们可以再以后的某个时刻恢复以前的状态，这好像是到目前为止第一个没有用到继承的模式