CS616: Software Engineering Spring 2009

1. CS616: Software Engineering Spring 2009 Design Patterns Sami Taha

2. Content • Introduction • Classification of patterns • List of patterns • GoF Patterns Template • Case Study: Observer pattern

3. Introduction • Design reuse • Design Patterns motivation

4. Classification of patterns • Creational patterns the process of object creation • Singleton • Single instance • Factory Method • Building • Prototype

5. Structural patterns deal with the composition of classes or objects • Façade • Unified interface • Proxy • Protection • Synchronization • Count references • Cache • Bridge • Composite

6. Behavioral patterns The ways classes or objects interact and distribute responsibility • Observer • Visitor • State • Command • Strategy • Chain of Responsibility • Interpreter • Integrator • Mediator • Memento • Template Method

7. GoF Patterns Template • Pattern Name and classification • Intent • What the pattern does • Motivation • Scenario where the pattern would be useful • Applicability • Situations to apply the design pattern • Structure • Graphical representation • Participants • Classes/object participating and responsibilities

8. GoF Patterns Template cont. • Collaborations • How the participants collaborates • Consequences • Pros and consequences • Implementation • Pitfalls, hints, or techniques should you be aware of • Sample Code and Usage • Code fragment • Known uses • Examples in real systems

9. Case Study • Observer Pattern • Pattern classification • Behavioral pattern • Motivation • Applicability • When a change to one object requires changing others • When an object should be able to notify other objects

10. Case Study cont.. • Structure

11. Case Study cont.. • Known uses The observer pattern is implemented in many programming libraries specially GUI toolkits Examples Java Swing Boost.Signals QT Signal/Slot Library .Net remoting The standard PHP library

12. References • Wikipedia • http://www.cs.mum.edu/