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Design (a)

Design (b)

Design (c)

i.Book copies in a library ii.TV drama episodes iii.Video copies in a rental shop

i.Book copies in a library ii.TV drama episodes iii.Video copies in a rental shop

i.Book copies in a library ii.TV drama episodes iii.Video copies in a rental shop  

i.Book copies in a library ii.TV drama episodes iii.Video copies in a rental shop   Recurring tasks in a schedule

i.Book copies in a library ii.TV drama episodes iii.Video copies in a rental shop Recurring tasks in a schedule

Déjà vu: Using patterns to solve recurring problems CS2103/T, Lecture 8, Part 1, [Oct 11, 2013]

Déjà vu: Using patterns to solve recurring problems

experience Déjà vu: Using patterns to solve recurring problems

experience … is what you get when you didn’t get what you wanted.

… is valuable. experience

… is too costly. experience Learning from

experience Learning from Note to self: never volunteer to be the headstand guy

experience Learning from Patterns

Context: Multiple stock items of same TV model Problem: Same data (but not all) shared among stock items of the same model. Solution: Represent TV model and TV stock item as different classes.

Context: Multiple stock items of same TV model Problem: Same data (but not all) shared among stock items of the same model. Solution: Represent TV model and TV stock item as different classes. i.Stock items ii.Book copies in a library iii.TV drama episodes iv.… i.Stock items ii.Book copies in a library iii.TV drama episodes iv.…

Context: Multiple stock items of same TV model Problem: Same data (but not all) shared among stock items of the same model. Solution: Represent TV model and TV stock item as different classes.

Context: Multiple occurrences of some abstraction Problem: Same data (but not all) shared among occurrences of the same abstraction. Solution: Represent abstraction and occurrences as different classes.

Context: Multiple occurrences of some abstraction Problem: Same data (but not all) shared among occurrences of the same abstraction. Solution: Represent abstraction and occurrences as different classes. > *

Context: Multiple occurrences of some abstraction Problem: Same data (but not all) shared among occurrences of the same abstraction. Solution: Represent abstraction and occurrences as different classes. > *

* TVModel TVStockItem * BookTitle BookCopy * Lesson LessonDelivery *

> * TVModel TVStockItem * BookTitle BookCopy * Lesson LessonDelivery *

Context: Multiple occurrences of some abstraction Problem: Same data (but not all) shared among occurrences of the same abstraction. Solution: Represent abstraction and occurrences as different classes. Name: Abstraction Occurrence Pattern > *

Context: Multiple occurrences of some abstraction Problem: Same data (but not all) shared among occurrences of the same abstraction. Solution: Represent abstraction and occurrences as different classes. Name: Abstraction Occurrence Pattern > * [An elegant solution to a recurring problem]

Name: Abstraction Occurrence Pattern Context: Multiple occurrences of some abstraction Problem: Same data (but not all) shared among occurrences of the same abstraction. Solution: Represent abstraction and occurrences as different classes. > * [An elegant solution to a recurring problem]

Context: Multiple occurrences of some abstraction Problem: Same data (but not all) shared among occurrences of the same abstraction. Solution: Represent abstraction and occurrences as different classes. Name: Abstraction Occurrence Pattern > *

* Context: Multiple occurrences of some abstraction Problem: Same data (but not all) shared among occurrences of the same abstraction. Solution: Represent abstraction and occurrences as different classes. > * Show off ! … for that, I used the Name: Abstraction Occurrence Pattern

Patterns = a high-level vocabulary

Context: Multiple occurrences of some abstraction Problem: Same data (but not all) shared among occurrences of the same abstraction.

[A stupid solution to a recurring problem] Context: Multiple occurrences of some abstraction Problem: Same data (but not all) shared among occurrences of the same abstraction. Solution: Represent abstraction and occurrences as different classes.

[A stupid solution to a recurring problem] Context: Multiple occurrences of some abstraction Problem: Same data (but not all) shared among occurrences of the same abstraction. Solution: Represent abstraction and occurrences as different classes.

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer

Context: one-and-only-one object, shared among others

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer Context: one-and-only-one object, shared among others Problem: how to avoid multiple objects?

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer Logic - Logic( ) + getInstance( ) : Logic Solution:

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer Logic - theOne : Logic - Logic( ) + getInstance( ) : Logic Solution:

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer Logic - theOne : Logic - Logic( ) + getInstance( ) : Logic public static Logic getInstance(){ if (theOne == null) theOne = new Logic(); return theOne; } public static Logic getInstance(){ if (theOne == null) theOne = new Logic(); return theOne; } //somewhere else in the system… Logic m = Logic.getInstance(); //instead of … Logic m = new Logic(); //somewhere else in the system… Logic m = Logic.getInstance(); //instead of … Logic m = new Logic(); Solution:

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer Make everything static instead? a)OO ↓ b)Testability ↓ Logic UI LogicStub

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer

Logic - theOne : Logic - Logic( ) + getInstance( ) : Logic public static Logic getInstance(){ if (theOne == null) theOne = new Logic(); return theOne; } public static Logic getInstance(){ if (theOne == null) theOne = new Logic(); return theOne; } //somewhere else in the system… Logic m = Logic.getInstance(); //instead of … Logic m = new Logic(); //somewhere else in the system… Logic m = Logic.getInstance(); //instead of … Logic m = new Logic();

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer How many classes in your project can benefit from this pattern? a. None b. Only 1 c. Only 2 d. Only 3 e. 4 or more single {a|b|c|d|e} e.g. single c single {a|b|c|d|e} e.g. single c 77577

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer

ATD TextUI Logic

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer ATD TextUI MSLogic Logic

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer >

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer Edit Sort Delete

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer

Data objects UI elements Create/ edit/ delete/read

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer Data objects Create/ edit/ delete/read UI elements VIEW MODEL CONTROLLER

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer Data objects Create/ edit/ delete/read UI elements VIEW MODEL CONTROLLER

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer

Paparazzi Celebrity

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer Paparazzi Celebrity

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer Paparazzi Celebrity

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer Celebrity Paparazzi

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer ListUI Data SummaryUI = Observers AddUI = Observed Celebrity Paparazzi

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer > Observer > Observer ListUI update( ) Data +addViews(Observer) -notifyUIs( ) +addViews(Observer) -notifyUIs( ) * SummaryUI update( ) :Data :Observer = Observers AddUI = Observed

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer > Observer > Observer > update( ) > +add(Observer) -notifyObservers( ) +add(Observer) -notifyObservers( ) * > update( )

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer

Where? → Learning → Applying

Which way do I face? Window or the TV? Darn…

Where? → Learning → Applying

Christopher Alexander

Where? → Learning → Applying Abstraction occurrence  Analysis patterns Singleton  Design patterns MVC  Architectural patterns ….  Testing patterns ….  Project management patterns

Where? → Learning → Applying Abstraction occurrence  Analysis patterns Singleton  Design patterns MVC  Architectural patterns ….  Testing patterns ….  Project management patterns

Where? → Learning → Applying

Creational: Abstract Factory Builder Factory Method Prototype Singleton Creational: Abstract Factory Builder Factory Method Prototype Singleton Structural: Adapter Bridge Composite Decorator Façade Flyweight Proxy Structural: Adapter Bridge Composite Decorator Façade Flyweight Proxy Behavioral : Chain of Responsibility Command Interpreter Template Method Iterator Memento State Visitor Mediator Observer Strategy Behavioral : Chain of Responsibility Command Interpreter Template Method Iterator Memento State Visitor Mediator Observer Strategy GoF patterns

Where? → Learning → Applying

So many patterns, so little time…

Where? → Learning → Applying So many patterns, so little time…

Where? → Learning → Applying So many patterns, so little time…

Where? → Learning → Applying Can apply Singleton in your project?

Where? → Learning → Applying

Part 1 - Déjà vu: Using patterns to solve recurring problems.

1. Abstraction occurrence 2. Singleton 3. Façade 4. Command 5. MVC 6.Observer 7. …… [by next tutorial]

What are the negative consequence of applying the façade pattern? a. Extra code. b. Slower performance. c. Both of the above. d. No negative consequences. negative {a|b|c|d} e.g. negative c negative {a|b|c|d} e.g. negative c 77577