C++怎么实现一个职责链模式_C++使多个对象都有机会处理请求的解耦模式

#include <iostream>
#include <string>

// 抽象处理者
class Handler {
protected:
    Handler* nextHandler;

public:
    Handler() : nextHandler(nullptr) {}

    void setNext(Handler* handler) {
        nextHandler = handler;
    }

    virtual ~Handler() = default;

    // 处理请求，子类可重写
    virtual void handleRequest(const std::string& request) {
        if (nextHandler) {
            nextHandler->handleRequest(request);
        } else {
            std::cout << "No handler can process: " << request << std::endl;
        }
    }
};

// 具体处理者A
class ConcreteHandlerA : public Handler {
public:
    void handleRequest(const std::string& request) override {
        if (request == "A") {
            std::cout << "ConcreteHandlerA handled request: " << request << std::endl;
        } else {
            Handler::handleRequest(request); // 转发
        }
    }
};

// 具体处理者B
class ConcreteHandlerB : public Handler {
public:
    void handleRequest(const std::string& request) override {
        if (request == "B") {
            std::cout << "ConcreteHandlerB handled request: " << request << std::endl;
        } else {
            Handler::handleRequest(request);
        }
    }
};

int main() {
    ConcreteHandlerA handlerA;
    ConcreteHandlerB handlerB;

    // 构建链：A -> B
    handlerA.setNext(&handlerB);

    // 发送请求
    handlerA.handleRequest("A"); // A处理
    handlerA.handleRequest("B"); // A无法处理，转给B
    handlerA.handleRequest("C"); // 都无法处理

    return 0;
}

ConcreteHandlerA handled request: A
ConcreteHandlerB handled request: B
No handler can process: C