GOF pattern - Prototype - 毒菇求Buy

GOF pattern - Prototype

Definition

Specify the kind of objects to create using a prototypical instance, and create new objects by copying this prototype.

Frequency of use:

medium low

UML class diagram

Participants

The classes and/or objects participating in the Prototype pattern are:

Prototype (ColorPrototype)
- declares an interace for cloning itself
ConcretePrototype (Color)
- implements an operation for cloning itself
Client (ColorManager)
- creates a new object by asking a prototype to clone itself

Sample code

This structural code demonstrates the Prototype pattern in which new objects are created by copying pre-existing objects (prototypes) of the same class.

// Prototype pattern -- Structural example

//--------------------------------------------------------
// Copyright (C) 2001 - 2002, Data & Object Factory
// All rights reserved. www.dofactory.com
//
// You are free to use this source code in your
// applications as long as the original copyright
// notice is included.
//
// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT
// WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF
// MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
//--------------------------------------------------------

using System;

// "Prototype"
abstract class Prototype {
  // Fields
  private string id;

  // Constructors
  public Prototype( string id ) {
    this.id = id;
  }

  public string Id {
    get{ return id; }
  }

  // Methods
  abstract public Prototype Clone();
}

// "ConcretePrototype1"
class ConcretePrototype1 : Prototype {
  // Constructors
  public ConcretePrototype1( string id ) : base ( id ) {}

  // Methods
  override public Prototype Clone() {
    // Shallow copy
    return (Prototype)this.MemberwiseClone();
  }
}

// "ConcretePrototype2"
class ConcretePrototype2 : Prototype {
  // Constructors
  public ConcretePrototype2( string id ) : base ( id ) {}

  // Methods
  override public Prototype Clone() {
    // Shallow copy
    return (Prototype)this.MemberwiseClone();
  }
}

/// <summary>
///   Client test
/// </summary>
class Client {
  public static void Main( string[] args ) {
    // Create two instances and clone each
    ConcretePrototype1 p1 = new ConcretePrototype1("I");
    ConcretePrototype1 c1 = (ConcretePrototype1)p1.Clone();
    Console.WriteLine( "Cloned: {0}", c1.Id );

    ConcretePrototype2 p2 = new ConcretePrototype2("II");
    ConcretePrototype2 c2 = (ConcretePrototype2)p2.Clone();
    Console.WriteLine( "Cloned: {0}", c2.Id );
  }
}

This real-world code demonstrates the Prototype pattern in which new Color objects are created by copying pre-existing, user-defined Colors of the same type.

// Prototype pattern -- Real World example

//--------------------------------------------------------
// Copyright (C) 2001 - 2002, Data & Object Factory
// All rights reserved. www.dofactory.com
//
// You are free to use this source code in your
// applications as long as the original copyright
// notice is included.
//
// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT
// WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF
// MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
//--------------------------------------------------------

using System;
using System.Collections;

// "Prototype"
abstract class ColorPrototype {
  // Methods
  public abstract ColorPrototype Clone();
}

// "ConcretePrototype"
class Color : ColorPrototype {
  // Fields
  private int red, green, blue;

  // Constructors
  public Color( int red, int green, int blue) {
    this.red = red;
    this.green = green;
    this.blue = blue;
  }

  // Methods
  public override ColorPrototype Clone() {
    // Creates a 'shallow copy'
    return (ColorPrototype) this.MemberwiseClone();
  }

  public void Display() {
    Console.WriteLine( "RGB values are: {0},{1},{2}",
                                     red, green, blue );
  }
}

// Prototype manager
class ColorManager {
  // Fields
  Hashtable colors = new Hashtable();

  // Indexers
  public ColorPrototype this[ string name ] {
    get{ return (ColorPrototype)colors[ name ]; }
    set{ colors.Add( name, value ); }
  }
}

/// <summary>
///  PrototypeApp test
/// </summary>
class PrototypeApp {
  public static void Main( string[] args ) {
    ColorManager colormanager = new ColorManager();

    // Initialize with standard colors
    colormanager[ "red" ] = new Color( 255, 0, 0 );
    colormanager[ "green" ] = new Color( 0, 255, 0 );
    colormanager[ "blue" ] = new Color( 0, 0, 255 );

    // User adds personalized colors
    colormanager[ "angry" ] = new Color( 255, 54, 0 );
    colormanager[ "peace" ] = new Color( 128, 211, 128 );
    colormanager[ "flame" ] = new Color( 211, 34, 20 );

    // User uses selected colors
    string colorName = "red";
    Color c1 = (Color)colormanager[ colorName ].Clone();
    c1.Display();

    colorName = "peace";
    Color c2 = (Color)colormanager[ colorName ].Clone();
    c2.Display();

    colorName = "flame";
    Color c3 = (Color)colormanager[ colorName ].Clone();
    c3.Display();

    Console.Read();
  }
}

posted on 2005-07-07 08:19 毒菇求Buy 阅读(239) 评论(0) 编辑收藏引用所属分类: Design Pattern 、C#

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GOF pattern - Prototype

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