设计模式-职责链模式(C++)

职责链模式：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，并沿着这条链传递该请求，直到有一个对象处理它为止。

使用场景

1、有多个对象可以处理同一个请求

2、在不明确指定接收者的情况下，向多个对象中的提交请求

3、可动态指定一组对象处理请求

考虑员工要求加薪。公司的管理者一共有三级，总经理、总监、经理，如果一个员工要求加薪，应该向主管的经理申请，如果加薪的数量在经理的职权内，那么经理可以直接批准，否则将申请上交给总监。总监的处理方式也一样，总经理可以处理所有请求。这就是典型的职责链模式，请求的处理形成了一条链，直到有一个对象处理请求。

#include<iostream>
#include<cstring>

using namespace std;

class Manager
{
protected:
    Manager * m_manager;
    string m_name;
public:
    Manager(Manager * manager, string name):m_manager(manager),m_name(name){}
    virtual void DealWithRequest(string name, int num) {}
};

class CommonManager : public Manager
{
public:
    CommonManager(Manager * manager, string name):Manager(manager, name){}
    void DealWithRequest(string name, int num)
    {
        if(num < 500)
        {
            cout << m_name << " allow:" << name << " add:" << num << endl;
        }
        else
        {
            cout << name << " can not handle " << endl;
            m_manager->DealWithRequest(name, num);
        }
    }
};

class Majordomo : public Manager
{
public:
    Majordomo(Manager * manager, string name):Manager(manager, name) {}
    void DealWithRequest(string name, int num)
    {
        if(num < 1000)
        {
            cout << m_name << " allow:" << name << " add:" << num << endl;
        }
        else
        {
            cout << m_name << " can not handle " << endl;
            m_manager->DealWithRequest(name, num);
        }
    }
};

class GeneralManager : public Manager
{
public:
    GeneralManager(Manager * manager, string name):Manager(manager, name) {}
    void DealWithRequest(string name, int num)
    {
        cout << m_name << " allow:" << name << " add:" << num << endl;
    }
};

int main()
{
    Manager *general = new GeneralManager(NULL, "A"); //设置上级，总经理没有上级  
    Manager *majordomo = new Majordomo(general, "B"); //设置上级  
    Manager *common = new CommonManager(majordomo, "C"); //设置上级  
    common->DealWithRequest("D",300);  
    common->DealWithRequest("E", 600);  
    common->DealWithRequest("F", 1000);  
    delete common; delete majordomo; delete general;      
    return 0;
}