职责链（Chain of Responsibility）模式
participants
The classes and/or objects participating in this pattern are:
- Handler (Approver)
- defines an interface for handling the requests
- (optional) implements the successor link
- ConcreteHandler (Director, VicePresident, President)
- handles requests it is responsible for
- can access its successor
- if the ConcreteHandler can handle the request, it does so; otherwise it forwards the request to its successor
- Client (ChainApp)
- initiates the request to a ConcreteHandler object on the chain
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace ChainOfResponsibil
{
class Program
{
static void Main(string[] args)
{
Approver larry = new Director();
Approver sam = new VicePresident();
Approver tammy = new President();
larry.SetSuccessor(sam);
sam.SetSuccessor(tammy);
// Generate and process purchase requests
Purchase p = new Purchase(2034, 99999.00, "Supplies");
larry.ProcessRequest(p);
// Wait for user
Console.ReadKey();
}
}
abstract class Approver
{
protected Approver successor;
public void SetSuccessor(Approver successor)
{
this.successor = successor;
}
public abstract void ProcessRequest(Purchase purchase);
}
/// <summary>
/// The 'ConcreteHandler' class
/// </summary>
class Director : Approver
{
public override void ProcessRequest(Purchase purchase)
{
if (purchase.Amount < 10000.0)
{
Console.WriteLine("{0} approved request# {1}",
this.GetType().Name, purchase.Number);
}
else if (successor != null)
{
Console.WriteLine(this.GetType().Name + "---->" + successor.GetType().Name);
successor.ProcessRequest(purchase);
}
}
}
/// <summary>
/// The 'ConcreteHandler' class
/// </summary>
class VicePresident : Approver
{
public override void ProcessRequest(Purchase purchase)
{
if (purchase.Amount < 25000.0)
{
Console.WriteLine("{0} approved request# {1}",
this.GetType().Name, purchase.Number);
}
else if (successor != null)
{
Console.WriteLine(this.GetType().Name + "---->" + successor.GetType().Name);
successor.ProcessRequest(purchase);
}
}
}
/// <summary>
/// The 'ConcreteHandler' class
/// </summary>
class President : Approver
{
public override void ProcessRequest(Purchase purchase)
{
if (purchase.Amount < 100000.0)
{
Console.WriteLine("{0} approved request# {1}",
this.GetType().Name, purchase.Number);
}
else
{
Console.WriteLine(
"Request# {0} requires an executive meeting!",
purchase.Number);
}
}
}
/// <summary>
/// Class holding request details
/// </summary>
class Purchase
{
private int _number;
private double _amount;
private string _purpose;
// Constructor
public Purchase(int number, double amount, string purpose)
{
this._number = number;
this._amount = amount;
this._purpose = purpose;
}
// Gets or sets purchase number
public int Number
{
get { return _number; }
set { _number = value; }
}
// Gets or sets purchase amount
public double Amount
{
get { return _amount; }
set { _amount = value; }
}
// Gets or sets purchase purpose
public string Purpose
{
get { return _purpose; }
set { _purpose = value; }
}
}
}