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Chain of Responsibility

2,834 bytes added, 21:22, 2 April 2007
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=== C# Example ===
'''Example 1'''
Our command will be a PhoneCall class with one method "Converse()" which is our command.
*Hello. This is ACME Movie Rentals with an important message.
----
 
'''Example 2'''
 
using System;
 
namespace DoFactory.GangOfFour.Chain.RealWorld
 
{
 
// MainApp test application
 
class MainApp
{
static void Main()
{
// Setup Chain of Responsibility
Director Larry = new Director();
VicePresident Sam = new VicePresident();
President Tammy = new President();
Larry.SetSuccessor(Sam);
Sam.SetSuccessor(Tammy);
 
// Generate and process purchase requests
Purchase p = new Purchase(2034, 350.00, "Supplies");
Larry.ProcessRequest(p);
 
p = new Purchase(2035, 32590.10, "Project X");
Larry.ProcessRequest(p);
 
p = new Purchase(2036, 122100.00, "Project Y");
Larry.ProcessRequest(p);
 
// Wait for user
Console.Read();
}
}
 
// "Handler"
 
abstract class Approver
{
protected Approver successor;
 
public void SetSuccessor(Approver successor)
{
this.successor = successor;
}
 
public abstract void ProcessRequest(Purchase purchase);
}
 
// "ConcreteHandler"
 
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)
{
successor.ProcessRequest(purchase);
}
}
}
 
// "ConcreteHandler"
 
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)
{
successor.ProcessRequest(purchase);
}
}
}
 
// "ConcreteHandler"
 
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);
}
}
}
 
// Request details
 
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;
}
 
// Properties
public double Amount
{
get{ return amount; }
set{ amount = value; }
}
 
public string Purpose
{
get{ return purpose; }
set{ purpose = value; }
}
 
public int Number
{
get{ return number; }
set{ number = value; }
}
}
}
----
1
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