Prototype

UML class diagram

Participants
The classes and 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
Structural 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.
using System;
namespace DoFactory.GangOfFour.Prototype.Structural
{
/// <summary>
/// MainApp startup class for Structural
/// Prototype Design Pattern.
/// </summary>
class MainApp
{
/// <summary>
/// Entry point into console application.
/// </summary>
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.ReadKey();
}
}
/// <summary>
/// The 'Prototype' abstract class
/// </summary>
abstract class Prototype
{
private string _id;
// Constructor
public Prototype(string id)
{
this._id = id;
}
// Gets id
public string Id
{
get { return _id; }
}
public abstract Prototype Clone();
}
/// <summary>
/// A 'ConcretePrototype' class
/// </summary>
class ConcretePrototype1 : Prototype
{
// Constructor
public ConcretePrototype1(string id)
: base(id)
{
}
// Returns a shallow copy
public override Prototype Clone()
{
return (Prototype)this.MemberwiseClone();
}
}
/// <summary>
/// A 'ConcretePrototype' class
/// </summary>
class ConcretePrototype2 : Prototype
{
// Constructor
public ConcretePrototype2(string id)
: base(id)
{
}
// Returns a shallow copy
public override Prototype Clone()
{
return (Prototype)this.MemberwiseClone();
}
}
}
Output
Cloned: II
Real-world code in C#
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.Generic;
namespace DoFactory.GangOfFour.Prototype.RealWorld
{
/// <summary>
/// MainApp startup class for Real-World
/// Prototype Design Pattern.
/// </summary>
class MainApp
{
/// <summary>
/// Entry point into console application.
/// </summary>
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);
// User clones selected colors
Color color1 = colormanager["red"].Clone() as Color;
Color color2 = colormanager["peace"].Clone() as Color;
Color color3 = colormanager["flame"].Clone() as Color;
// Wait for user
Console.ReadKey();
}
}
/// <summary>
/// The 'Prototype' abstract class
/// </summary>
abstract class ColorPrototype
{
public abstract ColorPrototype Clone();
}
/// <summary>
/// The 'ConcretePrototype' class
/// </summary>
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;
}
}
/// <summary>
/// Prototype manager
/// </summary>
class ColorManager
{
private Dictionary<string, ColorPrototype> _colors =
new Dictionary<string, ColorPrototype>();
// Indexer
public ColorPrototype this[string key]
{
get { return _colors[key]; }
set { _colors.Add(key, value); }
}
}
}
Output
Cloning color RGB: 128,211,128
Cloning color RGB: 211, 34, 20
.NET Optimized code in C#
The .NET optimized code demonstrates the
same real-world situation as above but uses modern, built-in .NET features,
such as, generics, reflection, LINQ, lambda functions, and more.
You can find an example on our Singleton pattern page.
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