C++中的备忘录模式

实际应用

文本编辑器的撤销功能

游戏角色状态保存和恢复

图形编辑器的撤销/重做功能

总结

备忘录模式（Memento Pattern）

备忘录模式是一种行为型设计模式，它允许在不破坏封装性的前提下捕获和恢复对象的内部状态。这个模式的主要目的是保存对象的某个状态，以便在适当的时候恢复对象到之前的状态。备忘录模式主要包含三个角色：
1. Originator：负责创建一个备忘录（Memento），用以记录当前的内部状态，并在需要时使用备忘录恢复内部状态。
2. Memento：备忘录，负责存储Originator的内部状态。
3. Caretaker：负责保存备忘录，但不能对备忘录的内容进行操作或检查。

实际应用

文本编辑器的撤销功能

-- 文本编辑器，支持撤销操作。

#include <iostream>
#include <vector>
#include <string>// Memento类，用于存储文本编辑器的状态
class Memento {
private:std::string state;public:Memento(const std::string& state) : state(state) {}std::string getState() const { return state; }
};// Originator类，表示文本编辑器
class TextEditor {
private:std::string text;public:void write(const std::string& words) {text += words;}std::string getText() const {return text;}Memento save() const {return Memento(text);}void restore(const Memento& memento) {text = memento.getState();}
};// Caretaker类，用于管理Memento
class Caretaker {
private:std::vector<Memento> history;public:void save(const Memento& memento) {history.push_back(memento);}Memento undo() {if (!history.empty()) {Memento memento = history.back();history.pop_back();return memento;}return Memento(""); // 返回空的Memento}
};// 客户端代码
int main() {TextEditor editor;Caretaker caretaker;editor.write("Hello ");caretaker.save(editor.save());editor.write("World!");caretaker.save(editor.save());std::cout << "Current Text: " << editor.getText() << std::endl;editor.restore(caretaker.undo());std::cout << "After Undo: " << editor.getText() << std::endl;editor.restore(caretaker.undo());std::cout << "After Undo: " << editor.getText() << std::endl;return 0;
}

游戏角色状态保存和恢复

-- 模拟一个游戏角色的状态保存和恢复功能。

#include <iostream>
#include <vector>
#include <string>// Memento类，用于存储游戏角色的状态
class Memento {
private:int health;int mana;int experience;public:Memento(int health, int mana, int experience): health(health), mana(mana), experience(experience) {}int getHealth() const { return health; }int getMana() const { return mana; }int getExperience() const { return experience; }
};// Originator类，表示游戏角色
class GameCharacter {
private:int health;int mana;int experience;public:GameCharacter(int health, int mana, int experience): health(health), mana(mana), experience(experience) {}void setState(int health, int mana, int experience) {this->health = health;this->mana = mana;this->experience = experience;}void displayState() const {std::cout << "Health: " << health << ", Mana: " << mana<< ", Experience: " << experience << std::endl;}Memento save() const {return Memento(health, mana, experience);}void restore(const Memento& memento) {health = memento.getHealth();mana = memento.getMana();experience = memento.getExperience();}
};// Caretaker类，用于管理Memento
class Caretaker {
private:std::vector<Memento> savepoints;public:void save(const Memento& memento) {savepoints.push_back(memento);}Memento load() {if (!savepoints.empty()) {Memento memento = savepoints.back();savepoints.pop_back();return memento;}return Memento(100, 100, 0); // 返回初始状态}
};// 客户端代码
int main() {GameCharacter character(100, 50, 0);Caretaker caretaker;character.displayState();caretaker.save(character.save());character.setState(80, 40, 10);character.displayState();caretaker.save(character.save());character.setState(50, 30, 20);character.displayState();character.restore(caretaker.load());character.displayState();character.restore(caretaker.load());character.displayState();return 0;
}

图形编辑器的撤销/重做功能

-- 图形编辑器，支持撤销和重做操作。

#include <iostream>
#include <vector>
#include <string>
#include <stack>// Memento类，用于存储图形编辑器的状态
class Memento {
private:std::vector<std::string> shapes;public:Memento(const std::vector<std::string>& shapes) : shapes(shapes) {}std::vector<std::string> getState() const { return shapes; }
};// Originator类，表示图形编辑器
class GraphicEditor {
private:std::vector<std::string> shapes;public:void addShape(const std::string& shape) {shapes.push_back(shape);}void displayShapes() const {for (const auto& shape : shapes) {std::cout << shape << " ";}std::cout << std::endl;}Memento save() const {return Memento(shapes);}void restore(const Memento& memento) {shapes = memento.getState();}
};// Caretaker类，用于管理Memento
class Caretaker {
private:std::stack<Memento> undoStack;std::stack<Memento> redoStack;public:void save(const Memento& memento) {undoStack.push(memento);while (!redoStack.empty()) {redoStack.pop();}}Memento undo() {if (!undoStack.empty()) {Memento memento = undoStack.top();undoStack.pop();redoStack.push(memento);return memento;}return Memento(std::vector<std::string>()); // 返回空的Memento}Memento redo() {if (!redoStack.empty()) {Memento memento = redoStack.top();redoStack.pop();undoStack.push(memento);return memento;}return Memento(std::vector<std::string>()); // 返回空的Memento}
};// 客户端代码
int main() {GraphicEditor editor;Caretaker caretaker;editor.addShape("Circle");caretaker.save(editor.save());editor.addShape("Square");caretaker.save(editor.save());editor.addShape("Triangle");caretaker.save(editor.save());std::cout << "Current Shapes: ";editor.displayShapes();editor.restore(caretaker.undo());std::cout << "After Undo: ";editor.displayShapes();editor.restore(caretaker.undo());std::cout << "After Undo: ";editor.displayShapes();editor.restore(caretaker.redo());std::cout << "After Redo: ";editor.displayShapes();editor.restore(caretaker.redo());std::cout << "After Redo: ";editor.displayShapes();return 0;
}