定義：使多個對象都有機會處理請求，從而避免請求的發送者和接收者之間的耦合關係。將這個對象連成一條鏈，並沿着這條鏈傳遞該請求，直到有一個對象處理它爲止。
好處：當客戶提交一個請求時，請求時沿鏈傳遞直至有一個ConcreteHandler對象負責處理它。這就使得接收者和發送者都沒有對方的明確信息，且鏈中的對象自己也並不知道鏈的結構。結果是職責鏈可簡化對象的相互連接，它們僅需保持一個指向其後繼者的引用，而不需保持它所有的候選接收者的引用。這就大大降低了耦合度了。由於式在客戶端來定義鏈的結構，也就是說，我可以隨時得增加或修改處理一個請求的結構。增強了給對象指派職責的靈活性。
結構圖：
基本代碼：
using System;
using System.Collections.Generic;
using System.Text;
namespace 職責鏈模式
{
class Program
{
static void Main(string[] args)
{
Handler h1 = new ConcreteHandler1();
Handler h2 = new ConcreteHandler2();
Handler h3 = new ConcreteHandler3();
h1.SetSuccessor(h2);
h2.SetSuccessor(h3);
int[] requests = { 2, 5, 14, 22, 18, 3, 27, 20 };
foreach (int request in requests)
{
h1.HandleRequest(request);
}
Console.Read();
}
}
abstract class Handler
{
protected Handler successor;
public void SetSuccessor(Handler successor)
{
this.successor = successor;
}
public abstract void HandleRequest(int request);
}
class ConcreteHandler1 : Handler
{
public override void HandleRequest(int request)
{
if (request >= 0 && request < 10)
{
Console.WriteLine("{0} 處理請求 {1}",
this.GetType().Name, request);
}
else if (successor != null)
{
successor.HandleRequest(request);
}
}
}
class ConcreteHandler2 : Handler
{
public override void HandleRequest(int request)
{
if (request >= 10 && request < 20)
{
Console.WriteLine("{0} 處理請求 {1}",
this.GetType().Name, request);
}
else if (successor != null)
{
successor.HandleRequest(request);
}
}
}
class ConcreteHandler3 : Handler
{
public override void HandleRequest(int request)
{
if (request >= 20 && request < 30)
{
Console.WriteLine("{0} 處理請求 {1}",
this.GetType().Name, request);
}
else if (successor != null)
{
successor.HandleRequest(request);
}
}
}
}
例子：
using System;
using System.Collections.Generic;
using System.Text;
namespace 職責鏈模式
{
class Program
{
static void Main(string[] args)
{
CommonManager jinli = new CommonManager("金利");
Majordomo zongjian = new Majordomo("宗劍");
GeneralManager zhongjingli = new GeneralManager("鍾精勵");
jinli.SetSuperior(zongjian);
zongjian.SetSuperior(zhongjingli);
Request request = new Request();
request.RequestType = "請假";
request.RequestContent = "小菜請假";
request.Number = 1;
jinli.RequestApplications(request);
Request request2 = new Request();
request2.RequestType = "請假";
request2.RequestContent = "小菜請假";
request2.Number = 4;
jinli.RequestApplications(request2);
Request request3 = new Request();
request3.RequestType = "加薪";
request3.RequestContent = "小菜請求加薪";
request3.Number = 500;
jinli.RequestApplications(request3);
Request request4 = new Request();
request4.RequestType = "加薪";
request4.RequestContent = "小菜請求加薪";
request4.Number = 1000;
jinli.RequestApplications(request4);
Console.Read();
}
}
//管理者
abstract class Manager
{
protected string name;
//管理者的上級
protected Manager superior;
public Manager(string name)
{
this.name = name;
}
//設置管理者的上級
public void SetSuperior(Manager superior)
{
this.superior = superior;
}
//申請請求
abstract public void RequestApplications(Request request);
}
//經理
class CommonManager : Manager
{
public CommonManager(string name)
: base(name)
{ }
public override void RequestApplications(Request request)
{
if (request.RequestType == "請假" && request.Number <= 2)
{
Console.WriteLine("{0}:{1} 數量{2} 被批准", name, request.RequestContent, request.Number);
}
else
{
if (superior != null)
superior.RequestApplications(request);
}
}
}
//總監
class Majordomo : Manager
{
public Majordomo(string name)
: base(name)
{ }
public override void RequestApplications(Request request)
{
if (request.RequestType == "請假" && request.Number <= 5)
{
Console.WriteLine("{0}:{1} 數量{2} 被批准", name, request.RequestContent, request.Number);
}
else
{
if (superior != null)
superior.RequestApplications(request);
}
}
}
//總經理
class GeneralManager : Manager
{
public GeneralManager(string name)
: base(name)
{ }
public override void RequestApplications(Request request)
{
if (request.RequestType == "請假")
{
Console.WriteLine("{0}:{1} 數量{2} 被批准", name, request.RequestContent, request.Number);
}
else if (request.RequestType == "加薪" && request.Number <= 500)
{
Console.WriteLine("{0}:{1} 數量{2} 被批准", name, request.RequestContent, request.Number);
}
else if (request.RequestType == "加薪" && request.Number > 500)
{
Console.WriteLine("{0}:{1} 數量{2} 再說吧", name, request.RequestContent, request.Number);
}
}
}
//申請
class Request
{
//申請類別
private string requestType;
public string RequestType
{
get { return requestType; }
set { requestType = value; }
}
//申請內容
private string requestContent;
public string RequestContent
{
get { return requestContent; }
set { requestContent = value; }
}
//數量
private int number;
public int Number
{
get { return number; }
set { number = value; }
}
}
}