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

2. Agenda – Lecture 11b DiceGame New GoF patterns. Exercise Set.
Summary of redesign done so far.
Relationship to patterns and principles.
New functionality.
New GoF patterns.
Exercise Set.
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3. What were the patterns we saw …
In our DiceGame redesign …
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4. Dice Game Refactoring We applied: Indirection principle.
Decoupled DiceGame from Dice by inserting an IDice interface in between.
Introduced a Simple Factory class, DiceFactory.
Made DiceFactory a Singleton.
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5. Dice Game: New Functionality
Although we added ConstDice we still have a
Problem:
Our DiceFactory only creates one type of IDice.
Solutions:
Somehow we want the behavior of createDice() to vary.
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6. DiceFactory.createDice().
Possible solutions:
DiceFactory can read a System property to determine the class to instantiate (Larman05, p.441).
Add a method to factory:
Generalize our solution further: Abstract Factory.
Any of these solutions will finally allow us to create our test class, … e.g.
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7. DiceGameTest JUnit TestCase
public void testWinning() {
int faceValue = 3;
DiceFactory.theOne().
DiceGame game = new DiceGame();
game.roll();
assertEquals("face value", faceValue, game.getFaceValue());
assertTrue("won", game.won()); }
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8. New Version of Dice Game
Support using a pair of Dice.
How can this be added?
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9. Multi-Dice Design
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10. Composite (Larman05, 26.8) Context/problem
How do you treat a group or composite structure of objects the same way (polymorphically) as a non-composite (atomic) object?
Solution
Define classes for composite and atomic objects so that they implement the same interface.
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11. Dice Composite
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12. Client Cannot Tell … SOEN 343, © P.Chalin,
DiceGame cannot tell whether it is dealing with one or more dice.
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13. Composite: Ex. Objects
Credits: GoF.
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14. Composite: Ex. Class Diagram
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15. Must “add” be implemented by Line?
In C++ add declared virtual; subclass need not implement it.
In Java if add is abstract, then subclasses must implement it.
String add(Graphic g) {
throw new UnsupportedOperationException(); }
Can you think of a better solution?
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16. Composite: Clients point-of-view
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17. Composite Pricing Strategies
Interface
Realization
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18. Patterns and Principles
We have (and still are) studying:
Larman’s GRASP
GoF
Fowler’s EA
The most fundamental are the principles.
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19. GRASP: Interrelationships
This is how Larman illustrates the interrelationships between the GRASP.
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20. Patterns apply principles, e.g. …
This is how Larman illustrates the interrelationships between the GRASP.
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21. Gang-of-four … a closer look
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22. Gang Of Four Gamma, Helm, Johnson, Vlissides
Some patterns covered in Larman, Chap. 23,…
All patterns in XDE
As documentation.
As dynamic templates.
Erich
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23. GoF Pattern Summary (& Relationhips)
[Picutre (c) GoF CD]
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24. GoF Pattern Classification
Behavioral Patterns
Creational Patterns
Structural Patterns
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25. GoF Behavioral Patterns
Chain of Responsibility
Command
Interpreter
Iterator
Mediator
Memento
Observer
State
Strategy
Template Method
Visitor
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26. GoF Creational Patterns
Abstract Factory
Builder
Factory Method (we saw Simple Factory)
Prototype
Singleton
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27. Factory
Context / problem: Who should be responsible for creating objects when there are special considerations, such as complex creation logic, a desire to separate the creation responsibilities for better cohesion, and so forth?
Solution: Create a Pure Fabrication object called a Factory.
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28. Factory Example SOEN 343, © P.Chalin,
Have we seen code like this anywhere?
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29. Larman’s comment on prev. figure
Note that the factory methods return objects types to an interfacre rather than a class so that the factory can return any implementation of the interface.
Factory methods can also
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30. (Abstract) Factory Example (GoF)
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31. FrontControllerServlet RemoveStudentCommand
Factory (in EAs)
FrontControllerServlet
FrontCommand
# processRequest ( )
+ init ( )
- getCommand ( ) : FrontCommand
+ processRequest ( )
- getCommandClass ( )
RemoveStudentCommand
ViewStudInfoCommand
+ processRequest ( )
+ processRequest ( )
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32. GoF Structural Patterns
Adapter
Bridge
Composite
Decorator
Facade
Flyweight
Proxy
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33. Adapter
Context / problem How to resolve incompatible interfaces, or provide a stable interface to similar components with different interfaces?
Solution: Convert the original interface of a component into another interface, through an intermediate adapter object.
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34. Adapter
Suppose we have a tax calculation class (or external library) but the interface is not well suited for our application.
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35. Adapter Adapter provides an interface suited to the application
GoodAsGoldTaxProAdapter
getTaxes( Sale ) : List of TaxLineItems
computeTax(…):double
GoodAsGoldTaxPro
Adapter provides an interface suited to the application
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36. Adapter (For More than One Class)
What if more than one class (library) needs to be adapted?
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37. Adapter
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