C++如何实现一个备忘录模式_C++设计模式之捕获对象状态并支持回滚

#include 
#include 
#include 

class Memento;

// 发起者：文本编辑器
class TextEditor {
private:
    std::string content;

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

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

    // 创建备忘录
    Memento createMemento() const;

    // 恢复状态
    void restoreFromMemento(const Memento& m);
};

// 备忘录类
class Memento {
    friend class TextEditor; // 允许TextEditor访问私有成员

private:
    std::string state;

    // 私有构造函数，仅发起者可创建
    Memento(const std::string& state) : state(state) {}

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

// 成员函数实现在Memento定义之后
Memento TextEditor::createMemento() const {
    return Memento(content);
}

void TextEditor::restoreFromMemento(const Memento& m) {
    content = m.state;
}

// 管理者：负责保存和恢复备忘录
class History {
private:
    std::stack snapshots;

public:
    void push(const Memento& m) {
        snapshots.push(m);
    }

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

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

int main() {
    TextEditor editor;
    History history;

    editor.write("Hello ");
    history.push(editor.createMemento()); // 保存状态

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

    editor.restoreFromMemento(history.pop()); // 撤销
    std::cout << "After undo: " << editor.getContent() << "\n";

    return 0;
}