SOEN 343 Software Design Computer Science and Software

SOEN 343 Software Design Computer Science and Software Engineering Department Concordia University Fall 2005 Instructor: Patrice Chalin SOEN 343, © P. Chalin SOEN 344, © P. Chalin

Agenda – Lecture 11 b • Dice. Game – Summary of redesign done so far. – Relationship to patterns and principles. – New functionality. • New Go. F patterns. • Exercise Set. 9/10/2020 SOEN 343, © P. Chalin, 2

What were the patterns we saw … • In our Dice. Game redesign … 9/10/2020 SOEN 343, © P. Chalin, 3

Dice Game Refactoring We applied: • Indirection principle. – Decoupled Dice. Game from Dice by inserting an IDice interface in between. • Introduced a Simple Factory class, Dice. Factory. • Made Dice. Factory a Singleton. 9/10/2020 SOEN 343, © P. Chalin, 4

Dice Game: New Functionality Although we added Const. Dice we still have a Problem: • Our Dice. Factory only creates one type of IDice. Solutions: • Somehow we want the behavior of create. Dice() to vary. 9/10/2020 SOEN 343, © P. Chalin, 5

Dice. Factory. create. Dice(). • Possible solutions: – Dice. Factory can read a System property to determine the class to instantiate (Larman 05, 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. 9/10/2020 SOEN 343, © P. Chalin, 6

Dice. Game. Test JUnit Test. Case public void test. Winning() { int face. Value = 3; Dice. Factory. the. One(). Dice. Game game = new Dice. Game(); game. roll(); assert. Equals("face value", face. Value, game. get. Face. Value()); assert. True("won", game. won()); 9/10/2020 SOEN 343, © P. Chalin, 7

New Version of Dice Game • Support using a pair of Dice. • How can this be added? 9/10/2020 SOEN 343, © P. Chalin, 8

Multi-Dice Design 9/10/2020 SOEN 343, © P. Chalin, 9

Composite (Larman 05, 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. 9/10/2020 SOEN 343, © P. Chalin, 10

Dice Composite 9/10/2020 SOEN 343, © P. Chalin, 11

Client Cannot Tell … 9/10/2020 SOEN 343, © P. Chalin, 12

Composite: Ex. Objects 9/10/2020 SOEN 343, © P. Chalin, 13

Composite: Ex. Class Diagram 9/10/2020 SOEN 343, © P. Chalin, 14

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 Unsupported. Operation. Exception(); } • Can you think of a better solution? 9/10/2020 SOEN 343, © P. Chalin, 15

Composite: Clients point-of-view 9/10/2020 SOEN 343, © P. Chalin, 16

Composite Pricing Strategies • Interface • Realization 9/10/2020 SOEN 343, © P. Chalin, 17

Patterns and Principles We have (and still are) studying: • Larman’s GRASP • Go. F • Fowler’s EA The most fundamental are the principles. 9/10/2020 SOEN 343, © P. Chalin, 18

GRASP: Interrelationships 9/10/2020 SOEN 343, © P. Chalin, 19

Patterns apply principles, e. g. … 9/10/2020 SOEN 343, © P. Chalin, 20

Gang-of-four … a closer look 9/10/2020 SOEN 343, © P. Chalin, 21

Gang Of Four • Gamma, Helm, Johnson, Vlissides • Some patterns covered in Larman, Chap. 23, … • All patterns in XDE – As documentation. – As dynamic templates. 9/10/2020 SOEN 343, © P. Chalin, 22

Go. F Pattern Summary (& Relationhips) 9/10/2020 SOEN 343, © P. Chalin, 23

Go. F Pattern Classification • Behavioral Patterns • Creational Patterns • Structural Patterns 9/10/2020 SOEN 343, © P. Chalin, 24

Go. F Behavioral Patterns • Chain of Responsibility • Command • Interpreter • Iterator • Mediator • Memento 9/10/2020 • • • Observer State Strategy Template Method Visitor SOEN 343, © P. Chalin, 25

Go. F Creational Patterns • • • Abstract Factory Builder Factory Method (we saw Simple Factory) Prototype Singleton 9/10/2020 SOEN 343, © P. Chalin, 26

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. 9/10/2020 SOEN 343, © P. Chalin, 27

Factory Example 9/10/2020 SOEN 343, © P. Chalin, 28

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 9/10/2020 SOEN 343, © P. Chalin, 29

(Abstract) Factory Example (Go. F) 9/10/2020 SOEN 343, © P. Chalin, 30

Factory (in EAs) Front. Command Front. Controller. Servlet # process. Request ( ) - get. Command ( ) : Front. Command - get. Command. Class ( ) + init ( ) + process. Request ( ) Remove. Student. Command + process. Request ( ) 9/10/2020 View. Stud. Info. Command + process. Request ( ) SOEN 343, © P. Chalin, 31

Go. F Structural Patterns • • Adapter Bridge Composite Decorator Facade Flyweight Proxy 9/10/2020 SOEN 343, © P. Chalin, 32

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. 9/10/2020 SOEN 343, © P. Chalin, 33

Adapter • Suppose we have a tax calculation class (or external library) but the interface is not well suited for our application. 9/10/2020 SOEN 343, © P. Chalin, 34

Adapter • Adapter provides an interface suited to the application Good. As. Gold. Tax. Pro. Adapter get. Taxes( Sale ) : List of Tax. Line. Items Good. As. Gold. Tax. Pro compute. Tax(…): double 9/10/2020 SOEN 343, © P. Chalin, 35

Adapter (For More than One Class) • What if more than one class (library) needs to be adapted? 9/10/2020 SOEN 343, © P. Chalin, 36

Adapter 9/10/2020 SOEN 343, © P. Chalin, 37