备忘录模式

备忘录模式 当你需要让对象返回之前的状态时（例如，你的用户请求“撤销”），就使用备忘录模式（MementoPattern）

#include <iostream>

using namespace std;


struct GameMemento {
public:
    GameMemento() : state("") {}
    GameMemento(string state) {
        this->state = state;
    }
    string getState() {
        return state;
    }
    void setState(string state) {
        this->state = state;
    }
private:
    string state;
};

struct MasterGameObject {
public:
    MasterGameObject() : state("") {}
    string getState(void) {
        return state;
    }
    void setState(string state) {
        this->state = state;
    }
    GameMemento *createGameMemento() {
        return new GameMemento(state);
    }
    void restoreMemento(GameMemento *gameMemento) {
        this->setState(gameMemento->getState());
    }

private:
    string state;
};

struct Caretaker {
public:
    GameMemento *getGameMemento() {
        return &gameMemento;
    }
    void setGameMemento(GameMemento *gameMemento) {
        this->gameMemento = *gameMemento;
    }
private:
    GameMemento gameMemento;
};


int main(int argc, char **argv) {
    MasterGameObject *game = new MasterGameObject();
    game->setState("state 1");
    cout << "Initial state: " << game->getState() << endl;

    Caretaker *caretaker = new Caretaker();
    caretaker->setGameMemento(game->createGameMemento());

    game->setState("state 2");
    cout << "Changed state: " << game->getState() << endl;

    game->restoreMemento(caretaker->getGameMemento());
    cout << "Restored state: " << game->getState() << endl;
}