第24章职责链模式

一 概念

• 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。

二 UML图

• Handler 定义一个处理请示的接口
• ConcreteHandler1, ConcreteHandler2 具体处理类，处理它负责的请求，可访问它的后继者，如果可处理该请求，就处理之，否则就将该请求转发给它的后继者。

三 职责链的好处

• 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。结果是职责链可以简化对象的相互连接，他们仅保持一个指向后继者的引用，而不需要保持它所有的候选接收者的引用。
• 可以随时地增加或修改处理一个请求的结构，增强了给对象指派职责的灵活性。
• 不过也应当小心，一个请求极有可能到了链的末端都得不到处理，或者因为没有正确配置而得不到处理。

四 C++代码实现

#include "pch.h"
#include <iostream>
#include <string>
using namespace std;

class Request
{
public:
	void SetRequestType(string type)
	{
		this->m_requestType = type;
	}
	string GetRequestType()
	{
		return this->m_requestType;
	}
	void SetRequestContent(string content)
	{
		this->m_requestContent = content;
	}
	string GetRequestContent()
	{
		return this->m_requestContent;
	}
	void SetRequestNumber(int number)
	{
		this->m_number = number;
	}
	int GetRequestNumber() const
	{
		return this->m_number;
	}
private:
	string m_requestType;  //申请类别
	string m_requestContent;  //申请内容
	int m_number; //申请的数量
};

class Manager
{
public:
	Manager(string name)
	{
		this->m_name = name;
	}
	//设置管理者的上级
	void SetSuperior(Manager* superior)
	{
		this->m_superior = superior;
	}
	//申请请求
	virtual void RequestApplications(Request* request) = 0;
protected:
	string m_name;
	Manager* m_superior;  //管理者的上级
};
//经理
class CommonManager : public Manager
{
public:
	CommonManager(string str)
		:Manager(str)
	{

	}
	void RequestApplications(Request* request) override
	{
		//经理所能有的权限就是可准许下属两天内的假期
		if (request->GetRequestType() == "请假" && request->GetRequestNumber() <= 2)
		{
			cout << this->m_name << ' ' << request->GetRequestContent() << " 数量" << request->GetRequestNumber() << " 被批准" << endl;
		}
		else
		{
			//其余的请求都需要转到上级
			if (this->m_superior != nullptr)
			{
				this->m_superior->RequestApplications(request);
			}
		}
	}
};

//总监
class Majordomo : public Manager
{
public:
	Majordomo(string str)
		:Manager(str)
	{

	}
	void RequestApplications(Request* request) override
	{
		//经理所能有的权限就是可准许下属两天内的假期
		if (request->GetRequestType() == "请假" && request->GetRequestNumber() <= 5)
		{
			cout << this->m_name << ' ' << request->GetRequestContent() << " 数量" << request->GetRequestNumber() << " 被批准" << endl;
		}
		else
		{
			//其余的请求都需要转到上级
			if (this->m_superior != nullptr)
			{
				this->m_superior->RequestApplications(request);
			}
		}
	}
};

//总经理的权限是全部都需要处理
class GeneralManager : public Manager
{
public:
	GeneralManager(string str)
		:Manager(str)
	{

	}
	void RequestApplications(Request* request) override
	{
		//经理所能有的权限就是可准许下属两天内的假期
		if (request->GetRequestType() == "请假")
		{
			cout << this->m_name << ' ' << request->GetRequestContent() << " 数量" << request->GetRequestNumber() << " 被批准" << endl;
		}
		else if(request->GetRequestType() == "加薪" && request->GetRequestNumber() <= 500)
		{
			cout << this->m_name << ' ' << request->GetRequestContent() << " 数量" << request->GetRequestNumber() << " 被批准" << endl;
		}
		else if (request->GetRequestType() == "加薪" && request->GetRequestNumber() > 500)
		{
			cout << this->m_name << ' ' << request->GetRequestContent() << " 数量" << request->GetRequestNumber() << " 再说吧" << endl;
		}
	}
};
int main()
{
	CommonManager* jinli = new CommonManager("经理");
	Majordomo* zongjian = new Majordomo("总监");
	GeneralManager* zongjingli = new GeneralManager("总经理");
	//设置上级，完全可以根据实际需要来更改设置
	jinli->SetSuperior(zongjian);
	zongjian->SetSuperior(zongjingli);

	//	
	Request* request = new Request();
	request->SetRequestType("请假");
	request->SetRequestContent("小菜请假");
	request->SetRequestNumber(1);
	jinli->RequestApplications(request);

	Request* request2 = new Request();
	request2->SetRequestType("请假");
	request2->SetRequestContent("小菜请假");
	request2->SetRequestNumber(4);
	jinli->RequestApplications(request2);

	Request* request3 = new Request();
	request3->SetRequestType("加薪");
	request3->SetRequestContent("小菜加薪");
	request3->SetRequestNumber(400);
	jinli->RequestApplications(request3);

	Request* request4 = new Request();
	request4->SetRequestType("加薪");
	request4->SetRequestContent("小菜加薪");
	request4->SetRequestNumber(1000);
	jinli->RequestApplications(request4);

	return 0;
}