定义:责任链模式(Chain of Responsibility)是一种行为设计模式,它允许你将请求沿着处理者链进行传递。每个处理者都有机会处理请求,如果某个处理者不能处理该请求,则可以将请求传递给链中的下一个处理者。这个模式使得你可以在不修改现有代码结构的情况下,动态地添加或删除处理者,并且可以将请求和处理者解耦,使得请求可以发送给一系列的处理者而无需关心哪个处理者会实际处理它。
代码:
// 抽象处理者
class Handler {
public: virtual ~Handler() = default; // 设置下一个处理者 void setNext(std::shared_ptr<Handler> next) { this->nextHandler = next; } // 处理请求 void handleRequest(const std::string& request) { if (canHandle(request)) { handle(request); } else if (nextHandler) { nextHandler->handleRequest(request); } else { std::cout << "No handler could process the request: " << request << std::endl; } } protected: // 判断是否能处理请求 virtual bool canHandle(const std::string& request) const = 0; // 处理请求的具体实现 virtual void handle(const std::string& request) = 0; private: std::shared_ptr<Handler> nextHandler;
}; // 具体处理者A
class ConcreteHandlerA : public Handler {
protected: bool canHandle(const std::string& request) const override { return request == "RequestA"; } void handle(const std::string& request) override { std::cout << "ConcreteHandlerA handled request: " << request << std::endl; }
}; // 具体处理者B
class ConcreteHandlerB : public Handler {
protected: bool canHandle(const std::string& request) const override { return request == "RequestB"; } void handle(const std::string& request) override { std::cout << "ConcreteHandlerB handled request: " << request << std::endl; }
}; int main() { // 创建处理者 auto handlerA = std::make_shared<ConcreteHandlerA>(); auto handlerB = std::make_shared<ConcreteHandlerB>(); // 设置职责链 handlerA->setNext(handlerB); // 发送请求 handlerA->handleRequest("RequestA"); // ConcreteHandlerA handled request: RequestA handlerA->handleRequest("RequestB"); // ConcreteHandlerB handled request: RequestB handlerA->handleRequest("RequestC"); // No handler could process the request: RequestC return 0;
}