Flyweight Pattern Code Review

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Download Description:flyweight pattern download
.NET Framework:3.5
.NET Language:C#
Date Published:2009-07-01
Download Size:2,077 KB

Define the Pattern Interface and Handler Objects

Define the IFlyweight interface to be used as the "blueprint" for the main application classes.

public interface IFlyweight { Int32 Width { get; } Int32 Height { get; }
void Load(String filename); void Display(PaintEventArgs e, Int32 row, Int32 col); }

The Flyweight class (object) inherits from the IFlyweight interface and implements the Load() and Display() methods.

public class Flyweight : IFlyweight { private Image m_thumbNail; public Int32 Width { get; private set; } public Int32 Height { get; private set; }
public void Load(string filename) { this.m_thumbNail = new Bitmap(filename).GetThumbnailImage(100, 100, null, new IntPtr()); this.Width = this.m_thumbNail.Width; this.Height = this.m_thumbNail.Height; } public void Display(PaintEventArgs e, Int32 row, Int32 col) { e.Graphics.DrawImage(this.m_thumbNail, col, row, this.m_thumbNail.Width, this.m_thumbNail.Height); } }

The Load() method essentially takes a large object (image) and creates a smaller version of the object (thumbnail). The Display() method provides a means to view the smaller object (thumbnail).

Define the Flyweight Factory Object

The FlyweightFactory class manages a collection of IFlyweight objects.

class FlyweightFactory { Dictionary<String, IFlyweight> flyweights = new Dictionary<string, IFlyweight>();
public FlyweightFactory() { flyweights.Clear(); } public IFlyweight this[String index] { get { if (!flyweights.ContainsKey(index)) { flyweights[index] = new Flyweight(); } return (flyweights[index]); } } }