Flyweight Design Pattern

 definition
 UML diagram
 participants
 sample code in C#



definition

Use sharing to support large numbers of fine-grained objects efficiently.

Frequency of use:   low

UML class diagram


participants

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

  • Flyweight   (Character)
    • declares an interface through which flyweights can receive and act on extrinsic state.
  • ConcreteFlyweight   (CharacterA, CharacterB, ..., CharacterZ)
    • implements the Flyweight interface and adds storage for intrinsic state, if any. A ConcreteFlyweight object must be sharable. Any state it stores must be intrinsic, that is, it must be independent of the ConcreteFlyweight object's context.
  • UnsharedConcreteFlyweight   ( not used )
    • not all Flyweight subclasses need to be shared. The Flyweight interface enables sharing, but it doesn't enforce it. It is common for UnsharedConcreteFlyweight objects to have ConcreteFlyweight objects as children at some level in the flyweight object structure (as the Row and Column classes have).
  • FlyweightFactory   (CharacterFactory)
    • creates and manages flyweight objects
    • ensures that flyweight are shared properly. When a client requests a flyweight, the FlyweightFactory objects assets an existing instance or creates one, if none exists.
  • Client   (FlyweightApp)
    • maintains a reference to flyweight(s).
    • computes or stores the extrinsic state of flyweight(s).

sample code in C#

This structural code demonstrates the Flyweight pattern in which a relatively small number of objects is shared many times by different clients.

Show code

// Flyweight pattern -- Structural example




This real-world code demonstrates the Flyweight pattern in which a relatively small number of Character objects is shared many times by a document that has potentially many characters.

Show code

// Flyweight pattern -- Real World example




This .NET optimized code demonstrates the same real-world situation as above but uses modern, built-in .NET features, such as, generics, reflection, object initializers, automatic properties, etc.

Show code

// Flyweight pattern -- .NET optimized




   Better Code 
   Better Career 
   Better Lifestyle 


.NET
Design Pattern
Framework 4.5


 
C# and VB.NET


   Includes:

  Gang of Four Patterns
  Head First Patterns
  Enterprise Patterns
  Multi-Tier Patterns

  Repository Pattern
  Unit-of-Work Pattern
  CQRS Pattern
  Active Record Pattern

  Model View Controller
  Model View Presenter
  Model View ViewModel

  SparkTM RAD Platform
  Art Shop MVC Application
  Much more...

Click here for details

-- Instant Access --
Instant Download