Design Patterns - 03 Composite and Flyweight Pattern
- 1. 03 Composite and Flyweight PatternDesign Patterns© Prafulla Paraskar 2010
- 2. CompositeStructural Design Pattern© Prafulla Paraskar 2010
- 3. DefinitionThe composite pattern describes that a group of objects are to be treated in the same way as a single instance of an object.(wikipedia)© Prafulla Paraskar 2010
- 4. Composite Pattern – Explained (1/2)© Prafulla Paraskar 2010
- 5. Composite Pattern – Explained (2/2)Arranges structured hierarchies so that single components and groups of components can be treated in the same way.Makes easier to add new components.Makes client code simpler, since they do not have to know if they are dealing with one or more components.Typical operations on the components include add, remove, display, find and group.© Prafulla Paraskar 2010
- 6. Composite Pattern – UML Diagram© Prafulla Paraskar 2010
- 7. Composite Pattern – Real World SamplesFiles and folders in WindowsOrganization TreeArithmetic Expressions like (2 + 4) * ( 5 + 6)Generic containers in .NET framework like list, queue, stack help implement the composite pattern.© Prafulla Paraskar 2010
- 8. Composite Pattern – GuidelinesYou have :An irregular structure of objects and composites of the objects.You WantClients to ignore all but the essential differences between objects and composites of objects.
- 9. To treat all objects in a composite uniformly.© Prafulla Paraskar 2010
- 10. FlyweightStructural Design Pattern© Prafulla Paraskar 2010
- 11. DefinitionThe Flyweight pattern is a pattern for sharing objects, where each instance does not contain its own state but stores it externally. This allows efficient sharing of objects to save space when there are many instances but only a few different types. (James W. Cooper – C# Design Patterns)© Prafulla Paraskar 2010
- 12. Flyweight Pattern – Explained (1/3)Designing objects down to the lowest levels of system "granularity” provides optimal flexibility, but can be unacceptably expensive in termsRow objectsapparentRow objectsCharacter objectColumn object© Prafulla Paraskar 2010
- 13. Flyweight Pattern – Explained (2/3)columnrowrowrowafedcbglkjihFlyweight pool© Prafulla Paraskar 2010
- 14. Flyweight Pattern – Explained (3/3)Useful in cases where large number of objects (flyweights)required to provide “fine grain access” to the system. Characteristics of flyweights are divided into intrinsic (inseparable) e.g. identity and extrinsic (separable) e.g. shared resource.Shared resource is taken care by a directory which manages enrollment of participant and provides on demand access to shared resources.Flyweights can only be created with help of a factory to enforce enrollment and sharing of resources. © Prafulla Paraskar 2010
- 15. Flyweight Pattern – UML Diagram© Prafulla Paraskar 2010
- 16. Flyweight Pattern – Real World SamplesThumbnail representation of images in windows explorer. Order processing system where the items are relatively similar and differ only in certain characteristics.Representation of files and folders in windows explorer.Individual cells in a spreadsheet program. © Prafulla Paraskar 2010
- 17. Flyweight Pattern – GuidelinesWhen:May objects to deal with in memory
- 18. Different kinds of state, which can be handled differently to achieve space savings
- 19. Group of objects that share state
- 20. Ways of computing some of the state at runtime
- 21. The application doesn’t depend on object identityYou want to:Implement a system despite sever memory constraints© Prafulla Paraskar 2010
- 22. Thank you!http://geekswithblogs.net/technomadPresentation by Prafulla Paraskar prafulla.paraskar@s1.com© 2010 S1 India Pvt. Ltd.Presentation by Prafulla Paraskar eprafulla@gmail.com© 2010 Prafulla Paraskar