c++如何实现备忘录设计模式_c++ Memento模式与状态撤销

#include 
#include 
#include 

// 备忘录类：保存发起者的状态
class Memento {
    std::string state;
public:
    Memento(const std::string& s) : state(s) {}

    const std::string& getState() const {
        return state;
    }
};

// 发起者类：需要保存和恢复状态的对象
class Editor {
    std::string content;

public:
    void setContent(const std::string& text) {
        content = text;
    }

    std::string getContent() const {
        return content;
    }

    // 创建备忘录
    Memento save() const {
        return Memento(content);
    }

    // 从备忘录恢复状态
    void restore(const Memento& m) {
        content = m.getState();
    }
};

// 管理者类：管理多个备忘录（如实现多步撤销）
class History {
    std::stack states;
public:
    void push(const Memento& m) {
        states.push(m);
    }

    Memento pop() {
        if (states.empty()) {
            throw std::runtime_error("No saved states");
        }
        Memento m = states.top();
        states.pop();
        return m;
    }

    bool empty() const {
        return states.empty();
    }
};

int main() {
    Editor editor;
    History history;

    editor.setContent("First draft.");
    history.push(editor.save());  // 保存状态

    editor.setContent("Second draft.");
    history.push(editor.save());

    editor.setContent("Final version.");

    std::cout << "Current: " << editor.getContent() << "\n";

    // 撤销一次
    if (!history.empty()) {
        editor.restore(history.pop());
        std::cout << "After undo: " << editor.getContent() << "\n";
    }

    // 再次撤销
    if (!history.empty()) {
        editor.restore(history.pop());
        std::cout << "After second undo: " << editor.getContent() << "\n";
    }

    return 0;
}