C#说明设计模式（五） 创建型的OVER

原型模式:Prototype
Definition

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

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

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

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.


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();
  }
}