Third presentation of the multi part series. This one covering composite and flyweight pattern.

1. 03 Composite and Flyweight Pattern Design Patterns © Prafulla Paraskar 2010

2. Composite Structural Design Pattern © Prafulla Paraskar 2010

3. Definition The 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 Samples Files and folders in Windows Organization Tree Arithmetic Expressions like (2 + 4) * ( 5 + 6) Generic containers in .NET framework like list, queue, stack help implement the composite pattern. © Prafulla Paraskar 2010

9. To treat all objects in a composite uniformly.© Prafulla Paraskar 2010

10. Flyweight Structural Design Pattern © Prafulla Paraskar 2010

11. Definition The 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 terms Row objects a p p a r e n t Row objects Character object Column object © Prafulla Paraskar 2010

13. Flyweight Pattern – Explained (2/3) column row row row a f e d c b g l k j i h Flyweight 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 Samples Thumbnail 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

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

22. Thank you! http://geekswithblogs.net/technomad Presentation by Prafulla Paraskar prafulla.paraskar@s1.com © 2010 S1 India Pvt. Ltd. Presentation by Prafulla Paraskar eprafulla@gmail.com © 2010 Prafulla Paraskar