c++ 责任链模式

责任链模式（Chain of Responsibility）的目标是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。将这些对象连成一条链，并沿着这条链传递请求，直到有一个对象处理它为止。结构图为：



用一个采购的例子来说明，采购人员在进行采购前需经过上级部门的批准，对于不同金额的采购分别要由不同级别的上级才能审批，假设1万以内的采购需要主管批准，10万以内的需要主管向总经理申请批准，超过10万总经理向需董事长宴请批准，这时对于采购的审批过程就形成了一条责任链，对于不同的采购请求就需要一级一级的向上传递，并最终传递到最上级然后自行处理。

结构图如下：



实现代码：

//Processor.h

class Processor

{

public:

virtual ~Processor();

virtual void Request(double) = 0;

void SetSuccessor(Processor*);

protected:

Processor();

Processor* m_pProcessor;

};

//Processor.cpp

#include "stdafx.h"

#include "Processor.h"

Processor::Processor()

{

}

Processor::~Processor()

{

if(m_pProcessor != NULL)

{

delete m_pProcessor;

m_pProcessor = NULL;

}

}

void Processor::SetSuccessor(Processor* pProcessor)

{

m_pProcessor = pProcessor;

}

//Director.h

#include "Processor.h"

class Director : public Processor

{

public:

Director();

virtual ~Director();

void Request(double);

};

//Director.cpp

#include "stdafx.h"

#include "Director.h"

#include <iostream>

using namespace std;

Director::Director()

{

}

Director::~Director()

{

}

void Director::Request(double dAmount)

{

if(dAmount <= 10000)

{

cout << "主管审批了采购请求" << endl;

}

else

{

cout << "申请金额走出主管权限范围，需向总经理申请审批" << endl;

if(this->m_pProcessor != NULL)

{

m_pProcessor->Request(dAmount);

}

}

}

//Manager.h

#include "Processor.h"

class Manager : public Processor

{

public:

Manager();

virtual ~Manager();

void Request(double);

};

//Manager.cpp

#include "stdafx.h"

#include "Manager.h"

#include <iostream>

using namespace std;

Manager::Manager()

{

}

Manager::~Manager()

{

}

void Manager::Request(double dAmount)

{

if(dAmount <= 100000)

{

cout << "总经理审批了采购请求" << endl;

}

else

{

cout << "申请金额超出总经理权限范围，需向董事长申请审批" << endl;

if(this->m_pProcessor != NULL)

{

m_pProcessor->Request(dAmount);

}

}

}

//Chariman.h

#include "Processor.h"

class Chariman : public Processor

{

public:

Chariman();

virtual ~Chariman();

void Request(double);

};

//Chariman.cpp

#include "stdafx.h"

#include "Chariman.h"

#include <iostream>

using namespace std;

Chariman::Chariman()

{

}

Chariman::~Chariman()

{

}

void Chariman::Request(double dAmount)

{

cout << "董事长审批了采购请求" << endl;

}

//main.cpp

#include "stdafx.h"

#include "Processor.h"

#include "Director.h"

#include "Manager.h"

#include "Chariman.h"

int main(int argc, char* argv[])

{

Processor* pDirector = new Director;

Processor* pManager = new Manager;

Processor* pChariman = new Chariman;

pDirector->SetSuccessor(pManager);

pManager->SetSuccessor(pChariman);

pDirector->Request(10000000.00);

return 0;

}

代码中申请了超过10成的订购请求，于是各级别负责人一步一步向上级提交申请，并最终由最上层决定审批结果。

运行结果如下：

申请金额超出主管权限范围，需向总经理申请审批

申请金额超出总经理权限范围，需向董事长申请审批

董事长审批了采购请求