1. SOEN 343 Software Design
Computer Science and Software Engineering Department
Concordia University
Fall 2005
Instructor: Patrice Chalin

2. Agenda – Lecture 12a …
9/17/2018
SOEN 343, © P.Chalin,

3. Gang Of Four Gamma, Helm, Johnson, Vlissides
Some patterns covered in Larman, Chap. 23,…
All patterns in XDE
As documentation.
As dynamic templates.
Erich
9/17/2018
SOEN 343, © P.Chalin,

4. GoF Pattern Summary (& Relationhips)
[Picutre (c) GoF CD]
9/17/2018
SOEN 343, © P.Chalin,

5. GoF Pattern Classification
Behavioral Patterns
Creational Patterns
Structural Patterns
9/17/2018
SOEN 343, © P.Chalin,

6. GoF Behavioral Patterns
Chain of Responsibility
Command
Interpreter
Iterator
Mediator
Memento
Observer
State
Strategy
Template Method
Visitor
9/17/2018
SOEN 343, © P.Chalin,

7. GoF Creational Patterns
Abstract Factory
Builder
Factory Method (we saw Simple Factory)
Prototype
Singleton
9/17/2018
SOEN 343, © P.Chalin,

8. GoF Structural Patterns
Adapter
Bridge
Composite
Decorator
Facade
Flyweight
Proxy
9/17/2018
SOEN 343, © P.Chalin,

9. Facade
9/17/2018
SOEN 343, © P.Chalin,

10. Facade
9/17/2018
SOEN 343, © P.Chalin,

11. Singleton (Larman Section 23.4) XDE Patterns Singleton
- uniqueInstance : Singleton
- attribute
# Singleton( )
+ getUniqueInstance ( ) : Singleton
+ getAttr( )
9/17/2018
SOEN 343, © P.Chalin,

12. Strategy
Context / problem: How to design for varying, but related, algorithms or policies? How to design for the ability to change (even dynamically) these algorithms or policies?
Solution: Define each algorithm/policy/strategy in a separate class with a common interface
9/17/2018
SOEN 343, © P.Chalin,

13. Strategy
9/17/2018
SOEN 343, © P.Chalin,

14. How Do We Create a Strategy?
9/17/2018
SOEN 343, © P.Chalin,

15. Composite Larman 23.7 (but explanation intertwined with other pattern)
Context / problem: How to treat an aggregate structure of objects the same way as an atomic (non-aggregate) object?
Solution: Define classes for composite and atomic objects that implement the same interface.
9/17/2018
SOEN 343, © P.Chalin,

16. Observer Pattern
9/17/2018
SOEN 343, © P.Chalin,

17. Observer How shall we have the display be updated?
Why not … have the Sale inform the display when it changes value.
9/17/2018
SOEN 343, © P.Chalin,

18. What is Wrong With This?
9/17/2018
SOEN 343, © P.Chalin,

19. Observer Pattern
Context / Problem: Different kinds of subscriber objects are interested in the state changes or events of a publisher object, and want to react in their own way when the publisher generates the event. …
9/17/2018
SOEN 343, © P.Chalin,

20. Observer Pattern
Solution: Define a “subscriber” or “listener” interface. Subscribers implement this interface. The publisher can dynamically register subscribers who are interested in an event, and notify them when an event occurs.
Clarification: Publisher can dynamically process registration requests from subscribers.
9/17/2018
SOEN 343, © P.Chalin,

21. Observers: Illustration
Change requests go down – e.g. one cell in the spread sheet might be changed.
Notifications go up (upward dependencies are not ok)
9/17/2018
SOEN 343, © P.Chalin,

22. Observer Class Diagram
(Shown in class)
9/17/2018
SOEN 343, © P.Chalin,

23. Sale Example
9/17/2018
SOEN 343, © P.Chalin,

24. Observer Pattern (GoF book)
9/17/2018
SOEN 343, © P.Chalin,