设计模式之原型模式

Prototype Design Pattern

---

definition Specify the kind of objects to create using a prototypical instance, and create new objects by copying this prototype. Frequency of use:  nbsp;medium

UML class diagram

participants

    The classes and/or objects participating in this pattern are:

• Prototype  (ColorPrototype)
  • declares an interface 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 in C#

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

Hide code

// Prototype pattern -- Structural example

using System; namespace DoFactory.GangOfFour.Prototype.Structural {       // MainApp test application    class MainApp   {           static void Main()     {        // 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);        // Wait for user       Console.Read();     }   }    // "Prototype"    abstract class Prototype   {      private string id;      // Constructor      public Prototype( string id)     {        this.id = id;     }      // Property      public string Id     {        get{ return id; }     }      public abstract Prototype Clone();   }    // "ConcretePrototype1"    class ConcretePrototype1 : Prototype   {      // Constructor      public ConcretePrototype1( string id) : base(id)     {     }      public override Prototype Clone()     {        // Shallow copy        return (Prototype) this.MemberwiseClone();     }   }    // "ConcretePrototype2"    class ConcretePrototype2 : Prototype   {      // Constructor      public ConcretePrototype2( string id) : base(id)     {     }      public override Prototype Clone()     {        // Shallow copy        return (Prototype) this.MemberwiseClone();     }   } }

Output Cloned: I Cloned: II

---

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

using System; using System.Collections; namespace DoFactory.GangOfFour.Prototype.RealWorld {       // MainApp test application    class MainApp   {      static void Main()     {       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);       Color color;        // User uses selected colors        string name = "red";       color = colormanager[name].Clone() as Color;       name = "peace";       color = colormanager[name].Clone() as Color;       name = "flame";       color = colormanager[name].Clone() as Color;        // Wait for user       Console.Read();     }   }    // "Prototype"    abstract class ColorPrototype   {      public abstract ColorPrototype Clone();   }    // "ConcretePrototype"    class Color : ColorPrototype   {      private int red;      private int green;      private int blue;      // Constructor      public Color( int red, int green, int blue)     {        this.red = red;        this.green = green;        this.blue = blue;     }      // Create a shallow copy      public override ColorPrototype Clone()     {       Console.WriteLine(         "Cloning color RGB: {0,3},{1,3},{2,3}",         red, green, blue);        return this.MemberwiseClone() as ColorPrototype;     }   }    // Prototype manager    class ColorManager   {     Hashtable colors = new Hashtable();      // Indexer      public ColorPrototype this[ string name]     {        get       {          return colors[name] as ColorPrototype;       }        set       {         colors.Add(name, value);       }     }   } }

Output Cloning color RGB: 255,  0,  0 Cloning color RGB: 128,211,128 Cloning color RGB: 211, 34, 20