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

最新推荐文章于 2025-06-04 00:23:46 发布

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最新推荐文章于 2025-06-04 00:23:46 发布

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分类专栏：设计模式

本文链接：https://blog.youkuaiyun.com/cai0612123/article/details/39494207

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本文介绍了一种设计模式——责任链模式，通过实例演示了如何利用此模式降低软件中请求发送者与接收者间的耦合度。以不同级别的医院处理不同程度病患为例，展示了责任链模式的实现方式。

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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)