Decorator

// Decorator pattern -- Real World example

using System; using System.Collections; namespace DoFactory.GangOfFour.Decorator.RealWorld {    // MainApp test application    class MainApp   {      static void Main()     {        // Create book       Book book = new Book ("Worley", "Inside ASP.NET", 10);       book.Display();        // Create video       Video video = new Video ("Spielberg", "Jaws", 23, 92);       video.Display();        // Make video borrowable, then borrow and display       Console.WriteLine("\nMaking video borrowable:");       Borrowable borrowvideo = new Borrowable(video);       borrowvideo.BorrowItem("Customer #1");       borrowvideo.BorrowItem("Customer #2");       borrowvideo.Display();        // Wait for user       Console.Read();     }   }    // "Component"    abstract class LibraryItem   {      private int numCopies;      // Property      public int NumCopies     {        get{ return numCopies; }        set{ numCopies = value; }     }      public abstract void Display();   }    // "ConcreteComponent"    class Book : LibraryItem   {      private string author;      private string title;      // Constructor      public Book( string author, string title, int numCopies)     {        this.author = author;        this.title = title;        this.NumCopies = numCopies;     }      public override void Display()     {       Console.WriteLine("\nBook ------ ");       Console.WriteLine(" Author: {0}", author);       Console.WriteLine(" Title: {0}", title);       Console.WriteLine(" # Copies: {0}", NumCopies);     }   }    // "ConcreteComponent"    class Video : LibraryItem   {      private string director;      private string title;      private int playTime;      // Constructor      public Video( string director, string title,        int numCopies, int playTime)     {        this.director = director;        this.title = title;        this.NumCopies = numCopies;        this.playTime = playTime;     }      public override void Display()     {       Console.WriteLine("\nVideo ----- ");       Console.WriteLine(" Director: {0}", director);       Console.WriteLine(" Title: {0}", title);       Console.WriteLine(" # Copies: {0}", NumCopies);       Console.WriteLine(" Playtime: {0}\n", playTime);     }   }    // "Decorator"    abstract class Decorator : LibraryItem   {      protected LibraryItem libraryItem;      // Constructor      public Decorator(LibraryItem libraryItem)     {        this.libraryItem = libraryItem;     }      public override void Display()     {       libraryItem.Display();     }   }    // "ConcreteDecorator"    class Borrowable : Decorator   {      protected ArrayList borrowers = new ArrayList();      // Constructor      public Borrowable(LibraryItem libraryItem)       : base(libraryItem)     {     }      public void BorrowItem( string name)     {       borrowers.Add(name);       libraryItem.NumCopies--;     }      public void ReturnItem( string name)     {       borrowers.Remove(name);       libraryItem.NumCopies++;     }      public override void Display()     {        base.Display();               foreach ( string borrower in borrowers)       {         Console.WriteLine(" borrower: " + borrower);       }     }   } }