【C++】Chapter20：职责链模式

职责链模式（Chain of Responsibility）：使多个对象都有机会处理请求，从而避免请求的发送者和接收者之间的耦合关系。将这个对象连成一条链，并沿着这条链传递该请求，直到有一个对象处理它为止。

职责链的好处是当客户提交一个请求时，请求时沿链传递直至有一个ConcreteHandler对象负责处理它。这就使得接收者和发送者都没有对方的明确信息，且链中的对象自己也并不知道链的结构。结果是职责链可简化对象的相互连接，他们仅需保持一个指向其后继者的引用，而不需保持它所有的候选接收者的引用。由于是在客户端来定义链的结构，那么可以随时地增加或修理处理一个请求的结构。增强了给对象指派职责的灵活性。不过也要小心，一个请求极有可能到了链的末尾都得不到处理，或者因为没有正确的配置而得不到处理。

 

 

模式框架

工程结构：

（1）抽象处理请求接口类 Handler.h

（2）具体的处理请求类    ConcreteHandler.h

（3）客户端                   ChainApp.cpp

 

 

 

（1）抽象处理请求接口类 Handler.h

#ifndef _HANDLER_H_ #define _HANDLER_H_ class Handler { public: // 设置继任者 void setSuccessor(Handler* pSuccessor) { m_pSuccessor = pSuccessor; } // 处理请求的抽象方法 virtual void HandlerRequest(int nRequest) = 0; protected: Handler* m_pSuccessor; }; #endif// _HANDLER_H_ 

（2）具体的处理请求类    ConcreteHandler.h

#ifndef _CONCRETE_HANDLER_H_ #define _CONCRETE_HANDLER_H_ #include "Handler.h" #include <iostream> using namespace std; class ConcreteHandler1 : public Handler { public: virtual void HandlerRequest(int nRequest) { // 处理此请求0-10的 if (nRequest >= 0 && nRequest < 10) { cout << "ConcreteHandler1 处理请求" << nRequest << endl; } else if (NULL != m_pSuccessor)// 转移到下一个 { m_pSuccessor->HandlerRequest(nRequest); } } }; class ConcreteHandler2 : public Handler { public: virtual void HandlerRequest(int nRequest) { // 处理此请求10-20的 if (nRequest >= 10 && nRequest < 20) { cout << "ConcreteHandler2 处理请求" << nRequest << endl; } else if (NULL != m_pSuccessor)// 转移到下一个 { m_pSuccessor->HandlerRequest(nRequest); } } }; class ConcreteHandler3 : public Handler { public: virtual void HandlerRequest(int nRequest) { // 处理此请求20-30的 if (nRequest >= 20 && nRequest < 30) { cout << "ConcreteHandler3 处理请求" << nRequest << endl; } else if (NULL != m_pSuccessor)// 转移到下一个 { m_pSuccessor->HandlerRequest(nRequest); } } }; #endif// _CONCRETE_HANDLER_H_ 

（3）客户端                   ChainApp.cpp

 

// ChainApp.cpp : 定义控制台应用程序的入口点。 // #include "stdafx.h" #include "ConcreteHandler.h" void FreePtr(void* ptr) { if (NULL != ptr) { delete ptr; ptr = NULL; } } int _tmain(int argc, _TCHAR* argv[]) { Handler* pHandler1 = new ConcreteHandler1(); Handler* pHandler2 = new ConcreteHandler2(); Handler* pHandler3 = new ConcreteHandler3(); if (NULL != pHandler1 && NULL != pHandler2 && NULL != pHandler3) { // 设置职责链上家与下家 pHandler1->setSuccessor(pHandler2); pHandler2->setSuccessor(pHandler3); pHandler3->setSuccessor(NULL); int nRequest[] = {2, 5, 15, 19, 25, 36}; int n = (sizeof(nRequest) / sizeof(int)); for (int nEach = 0; nEach < (sizeof(nRequest) / sizeof(int)); nEach++) { pHandler1->HandlerRequest(nRequest[nEach]); } } system("pause"); FreePtr(pHandler3); FreePtr(pHandler2); FreePtr(pHandler1); return 0; }  

 

 

实际应用

工程结构：

（1）抽象处理请求接口类 Manager.h

（2）具体的处理请求类    ConcreteManager.h

（3）请求类                    Request.h

（4）客户端                    ChainApp2.cpp

 

 

 

（1）抽象处理请求接口类 Manager.h

#ifndef _MANAGER_H_ #define _MANAGER_H_ #include "Request.h" class Manager { public: Manager(const string& strName) { m_strName = strName; } // 设置管理者的上级 void SetSuperior(Manager* pSuperior) { m_Superior = pSuperior; } // 申请请求 virtual void RequestApp(const Request& request) = 0; protected: string m_strName; Manager* m_Superior; }; #endif// _MANAGER_H_ 

（2）具体的处理请求类    ConcreteManager.h

#ifndef _CONCRETE_MANAGER_H_ #define _CONCRETE_MANAGER_H_ #include "Manager.h" #include <iostream> using namespace std; // 经理类 class CommonManager : public Manager { public: CommonManager(const string& strName) : Manager(strName) , m_strName(strName) { } virtual void RequestApp(const Request& request) { if ((0 == (request.GetRequestType()).compare("请假")) && request.GetRequestNumber() <= 2) { cout << m_strName << ":" << request.GetRequestContent() << "数量" << request.GetRequestNumber() << "被批准" << endl; } else if (NULL != m_Superior) { m_Superior->RequestApp(request); } } private: string m_strName; }; // 总监类 class Inspector : public Manager { public: Inspector(const string& strName) : Manager(strName) , m_strName(strName) { } virtual void RequestApp(const Request& request) { if ((0 == (request.GetRequestType()).compare("请假")) && request.GetRequestNumber() <= 5) { cout << m_strName << ":" << request.GetRequestContent() << "数量" << request.GetRequestNumber() << "被批准" << endl; } else if (NULL != m_Superior) { m_Superior->RequestApp(request); } } private: string m_strName; }; // 总经理 class GeneralManager : public Manager { public: GeneralManager(const string& strName) : Manager(strName) , m_strName(strName) { } virtual void RequestApp(const Request& request) { if ((0 == (request.GetRequestType()).compare("请假")) && request.GetRequestNumber() <= 5) { cout << m_strName << ":" << request.GetRequestContent() << "数量" << request.GetRequestNumber() << "被批准" << endl; } else if ((0 == (request.GetRequestType()).compare("加薪")) && request.GetRequestNumber() <= 500) { cout << m_strName << ":" << request.GetRequestContent() << "数量" << request.GetRequestNumber() << "被批准" << endl; } else if ((0 == (request.GetRequestType()).compare("加薪")) && request.GetRequestNumber() > 500) { cout << m_strName << ":" << request.GetRequestContent() << "数量" << request.GetRequestNumber() << "再说吧" << endl; } } private: string m_strName; }; #endif// _CONCRETE_MANAGER_H_ 

（3）请求类                   Request.h

#ifndef _REQUEST_H_ #define _REQUEST_H_ #include <string> using namespace std; class Request { public: string GetRequestType(void) const { return m_strRequestType; } void SetRequestType(const string& strRequestType) { m_strRequestType = strRequestType; } string GetRequestContent(void) const { return m_strRequestContent; } void SetRequestContent(const string& strRequestContent) { m_strRequestContent = strRequestContent; } int GetRequestNumber(void) const { return m_nRequestNumber; } void SetRequestNumber(const int nRequestNumber) { m_nRequestNumber = nRequestNumber; } private: string m_strRequestType; string m_strRequestContent; int m_nRequestNumber; }; #endif// _REQUEST_H_ 

（4）客户端                   ChainApp2.cpp

// ChainApp2.cpp : 定义控制台应用程序的入口点。 // #include "stdafx.h" #include "ConcreteManager.h" void freePtr(void* ptr) { if (NULL != ptr) { delete ptr; ptr = NULL; } } int _tmain(int argc, _TCHAR* argv[]) { CommonManager* CM = new CommonManager("经理"); Inspector* In = new Inspector("总监"); GeneralManager*GM = new GeneralManager("总经理"); if (NULL != CM && NULL != In && NULL != GM) { // 设置完上级，完全可以根据实际需求来更改设置 CM->SetSuperior(In); In->SetSuperior(GM); Request request; request.SetRequestType("请假"); request.SetRequestContent("小王请假"); request.SetRequestNumber(1); CM->RequestApp(request); request.SetRequestType("请假"); request.SetRequestContent("小兰请假"); request.SetRequestNumber(4); CM->RequestApp(request); request.SetRequestType("加薪"); request.SetRequestContent("小王要求加薪"); request.SetRequestNumber(500); CM->RequestApp(request); request.SetRequestType("加薪"); request.SetRequestContent("小王要求加薪"); request.SetRequestNumber(1000); CM->RequestApp(request); system("pause"); freePtr(GM); freePtr(In); freePtr(CM); } return 0; }