C++如何实现命令模式 C++命令模式的设计与示例

#include <iostream>
#include <vector>

// Receiver
class Light {
public:
    void turnOn() {
        std::cout << "Light is ON" << std::endl;
    }

    void turnOff() {
        std::cout << "Light is OFF" << std::endl;
    }
};

// Command Interface
class Command {
public:
    virtual void execute() = 0;
    virtual ~Command() {}
};

// Concrete Command
class TurnOnCommand : public Command {
private:
    Light* light;

public:
    TurnOnCommand(Light* light) : light(light) {}

    void execute() override {
        light->turnOn();
    }
};

// Concrete Command
class TurnOffCommand : public Command {
private:
    Light* light;

public:
    TurnOffCommand(Light* light) : light(light) {}

    void execute() override {
        light->turnOff();
    }
};

// Invoker
class RemoteControl {
private:
    std::vector<Command*> commands;

public:
    void setCommand(Command* command) {
        commands.push_back(command);
    }

    void pressButton() {
        if (!commands.empty()) {
            commands.back()->execute();
            commands.pop_back(); // 执行后移除，简化示例
        } else {
            std::cout << "No command set" << std::endl;
        }
    }
};

int main() {
    Light* livingRoomLight = new Light();

    TurnOnCommand* turnOnCmd = new TurnOnCommand(livingRoomLight);
    TurnOffCommand* turnOffCmd = new TurnOffCommand(livingRoomLight);

    RemoteControl* remote = new RemoteControl();
    remote->setCommand(turnOnCmd);
    remote->setCommand(turnOffCmd);

    remote->pressButton(); // Light is OFF (因为后设置的是TurnOffCommand)
    remote->pressButton(); // Light is ON

    delete turnOnCmd;
    delete turnOffCmd;
    delete livingRoomLight;
    delete remote;

    return 0;
}

// Command Interface (with Undo)
class Command {
public:
    virtual void execute() = 0;
    virtual void undo() = 0; // 添加 undo 方法
    virtual ~Command() {}
};

// Concrete Command (with Undo)
class TurnOnCommand : public Command {
private:
    Light* light;
    bool previousState; // 记录之前的状态，以便 undo

public:
    TurnOnCommand(Light* light) : light(light), previousState(false) {}

    void execute() override {
        previousState = (/*假设Light有个getState()方法*/ false); // 实际应用中需要获取灯的当前状态
        light->turnOn();
    }

    void undo() override {
        if (previousState) {
            light->turnOn(); // 恢复到之前的状态（如果之前是开着的）
        } else {
            light->turnOff(); // 恢复到之前的状态（如果之前是关着的）
        }
    }
};

//Invoker (with Undo/Redo)
class RemoteControl {
private:
    std::vector<Command*> commandHistory;
    int currentCommandIndex = -1; // 指向当前执行的命令

public:
    void executeCommand(Command* command) {
        command->execute();
        if (currentCommandIndex < (int)commandHistory.size() - 1) {
            // 如果执行了undo之后的新命令，则清除后面的历史
            commandHistory.erase(commandHistory.begin() + currentCommandIndex + 1, commandHistory.end());
        }
        commandHistory.push_back(command);
        currentCommandIndex++;
    }

    void undo() {
        if (currentCommandIndex >= 0) {
            commandHistory[currentCommandIndex]->undo();
            currentCommandIndex--;
        }
    }

    void redo() {
        if (currentCommandIndex < (int)commandHistory.size() - 1) {
            currentCommandIndex++;
            commandHistory[currentCommandIndex]->execute();
        }
    }
};

int main() {
    Light* livingRoomLight = new Light();
    RemoteControl* remote = new RemoteControl();

    TurnOnCommand* turnOnCmd = new TurnOnCommand(livingRoomLight);
    TurnOffCommand* turnOffCmd = new TurnOffCommand(livingRoomLight);

    remote->executeCommand(turnOnCmd); // Light is ON
    remote->executeCommand(turnOffCmd); // Light is OFF

    remote->undo(); // Light is ON
    remote->undo(); // Light is OFF

    remote->redo(); // Light is ON
    remote->redo(); // Light is OFF

    delete turnOnCmd;
    delete turnOffCmd;
    delete livingRoomLight;
    delete remote;

    return 0;
}