行为设计模式---责任链模式(Chain of Responsibility)

责任链模式: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受者之间的耦合关系。

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他为止

责任链模式降低了请求的发送端和接收端之间的耦合，使多个对象都有机会处理这个请求。

一个链可以是一条线，一个树，也可以是一个环。

.e.g

CountryHospital  --> LittleSick

CityHospital     --> MiddleSick

ProvinceHospital --> BadSick

Chain.h

#ifndef _CHAIN_H_

#define _CHAIN_H_

#include <iostream>

enum SickGrade

{

    LittleSick, MiddleSick, BadSick

};

class Hospital

{

public:

    Hospital(Hospital *h = NULL);

    virtual ~Hospital() {}

    void setHospital(Hospital *h);

    Hospital * getHospital();

    virtual void curPatient(SickGrade s) = 0;

protected:

    Hospital *high_;

};

class CountryHospital : public Hospital

{

public:

     CountryHospital(Hospital *h);

     virtual ~CountryHospital() {}

     virtual void curPatient(SickGrade s);

};

class CityHospital : public Hospital

{

public:

     CityHospital(Hospital *h);

     virtual ~CityHospital() {}

     virtual void curPatient(SickGrade s);

};

class ProvinceHospital : public Hospital

{

public:

    virtual ~ProvinceHospital() {}

    virtual void curPatient(SickGrade s);

};

#endif

           

Chain.cpp

#include "Chain.h"

using std::cout;

using std::endl;

Hospital::Hospital(Hospital *h)

{

    high_ = h;

}

void Hospital::setHospital(Hospital *h)

{

     high_ = h;

}

Hospital * Hospital::getHospital()

{

     return high_;

}

CountryHospital::CountryHospital(Hospital *h) : Hospital(h)

{

}

void CountryHospital::curPatient(SickGrade s)

{

     if (LittleSick != s)

     {

         cout << "Sorry, we can only cure little sick" << endl;

         this->high_->curPatient(s);

     }

     else

        cout << "little sick is ok" << endl;

}

CityHospital::CityHospital(Hospital *h) : Hospital(h)

{

}

void CityHospital::curPatient(SickGrade s)

{

     if (MiddleSick != s)

     {

          cout << "Sorry, we can only cure middle sick" << endl;

          this->high_->curPatient(s);

     }

     else

        cout << "middle sick is ok" << endl;

}

void ProvinceHospital::curPatient(SickGrade s)

{

     if (BadSick != s)

     {

         cout << "Sorry, we can only cure bad sick" << endl;

         this->high_->curPatient(s);

     }

     else

         cout << "bad sick is ok" << endl;

}

main.cpp

#include "Chain.h"

int main()

{

        Hospital *province = new ProvinceHospital();

        Hospital *city = new CityHospital(province);

        Hospital *country = new CountryHospital(city);

        country->curPatient(BadSick);

        if (NULL != country)

        {

                delete country;

                country = NULL;

        }

        if (NULL != city)

        {

                delete city;

                city = NULL;

        }

        if (NULL != province)

        {

                delete province;

                province = NULL;

        }

        return 0;

}

Makefile

cc=g++

exe=main

obj= main.o Chain.o

$(exe): $(obj)

        $(cc) -g -o $(exe) $(obj)

main.o: main.cpp Chain.h

        $(cc) -g -c main.cpp

Chain.o: Chain.cpp Chain.h

        $(cc) -g -c Chain.cpp

clean:

        rm -rf *o $(exe)