1. Design Patterns Yes, they are important Robert Cotton April 23, 2009

2. Roadmap History of Design Patterns Explore some more common patterns Frameworks or Design Patterns? Discus the consequences of patterns

3. History Did not originate in Computer Science Thought up by Christopher Alexander Formalized for Computer Science by the 'Gang of Four' who wrote Design Patterns: Elements of Reusable Object-Oriented Software

4. Gang of Four Erich Gamma Richard Helm Ralph Johnson John Vlissides ** referred to as 'Gamma et al'

5. What is a Design Pattern Four elements Pattern Name Problem Solution Consequences

6. Common Patterns Abstract Factory Builder Chain of Responsibility Facade Iterator Observer Singleton

7. Design Patterns in Use Abstraction

8. Design Patterns in Use Iterator

9. Design Patterns in Use Singleton

10. Design Patterns in Use Observer

11. Three Major Categories Creational Patterns Structural Patterns Behavioral Patterns

12. Design Patterns vs. Frameworks Frameworks contain and utilize design patterns. Frameworks are not design patterns

13. Frameworks Which use Design Patterns? Spring MVC Symfony Zend Hibernate (NHibernate)‏ Castle Windor Ruby on Rails.... (all of them)‏

14. Why Use Patterns Promotes good software design Need coupling/decoupling? Need encapsulation? Need to handle events?

15. Not Always Better Does not guarantee better code Can be hard to implement Can be hard to maintain Can be hard to understand

16. Errors Implementing some Design Patterns can actual lead to more errors!!

17. Why Learn Them Often times frameworks seem to operate on sheer magic. Usually it is utilizing a specific framework. Become a better software engineer Become a more valuable employee Become a better coder.