备忘录模式

【1】什么是备忘录模式？

在不破坏封装性的前提下，捕获一个对象的内部状态，并在该对象之外保存这个状态。

这样就可以将该对象恢复到原先保存的状态。

【2】备忘录模式的代码示例：

代码示例如下：
#include <iostream>
#include <string>
#include <vector>
using namespace std;

class Memo
{
public:
    string state;
    Memo(string state)
    {
        this->state = state;
    }
};

class Originator
{
public:
    string state;
    void setMemo(Memo *memo)
    {
        state = memo->state;
    }
    Memo *createMemo()
    {
        return new Memo(state);
    }
    void show()
    {
        cout << state << endl;
    }
};    

class Caretaker
{
public:
    vector<Memo *> memo;
public:
    void save(Memo *memo)
    {
        (this->memo).push_back(memo);
    }
    Memo *getState(int i)
    {
        return memo[i];
    }
};
 
int main()
{
    Originator *og = new Originator();
    Caretaker *ct = new Caretaker(); 

    og->state = "on";
    og->show();    
    ct->save(og->createMemo());

    og->state = "off";
    og->show();
    ct->save(og->createMemo());

    og->state = "middle";
    og->show();
    ct->save(og->createMemo());

    og->setMemo( ct->getState(1) );
    og->show();

    return 0;
}
//Result:
/*
on
off
middle
off
*/