DevDay Da Nang 2016 featured a presentation by Tuan on design patterns, explaining their definition and advantages for software development. Key patterns discussed included Abstract Factory, Factory Method, Adapter, Composite, Decorator, Observer, Strategy, and Template Method, each with its own unique functionality and use cases. The presentation emphasized the importance of design patterns in building well-structured, maintainable, and scalable software systems.

2. Welcome to DEVDAY
Da Nang 2016

3. I’m Tuan
• Live in Da Nang.
• Working in Axon Active
Vietnam.
• 6 years in development
• Scrum Master, Team Leader,
Software Engineer.
• Java, Javascript, Code
Generator. tuan.do@axonactive.com

4. Questions
• Who joined Devday Da Nang 2015 ?
• Who knows about refactoring ?
• Who knows about clean code ?

5. Design Pattern
at a glance
–Do Minh Tuan

6. What is a design pattern ?
“Each pattern describes a problem which occurs over
and over again in our environment, and then describes
the core of the solution to that problem, in such a way
that you can use this solution a million times over,
without ever doing it the same way twice”
- Christopher Wolfgang
Alexander (1936)

7. Elements of Pattern
The pattern name The problem
The consequences The solution
PATTERN

8. Advantages of Pattern
• Enhances code readability.
• Robust, Scalable.
• Enhances software development.
• Well-structured system.
• Well-tested system.

9. Ready for change

10. Gift Question

11. Organize the catalog

12. Design pattern relationship

13. How to select a design
pattern

14. How design patterns solve
design problems
• Finding appropriate objects.
• Determining Object Granularity.
• Specifying Object Interfaces.
• Specifying Object Implementations.

15. How to use a design pattern
(1 of 2)
• Read the pattern.
• Study the structure, participants and
collaborations sections.
• Sample code of pattern
• Choose names for pattern participants that are
meaningful in the application context.

16. How to use a design pattern
(2 of 2)
• Define the classes.
• Define application-specific names for operations
in the pattern.
• Implement the operations to carry out the
responsibillities and collaborations in the
pattern.

18. “Famous” Patterns
• Creational
• Abstract Factory
• Factory Method
• Structural
• Adapter
• Composite
• Decorator
• Behavioral
• Observer
• Strategy
• Template Method

19. “Famous” Patterns
• Creational
• Abstract Factory
• Factory Method
• Structural
• Adapter
• Composite
• Decorator
• Behavioral
• Observer
• Strategy
• Template Method

20. Abstract Factory
“Provide an interface for creating families of
related or dependent objects without specifying
their concrete classes.”

22. “Famous” Patterns
• Creational
• Abstract Factory
• Factory Method
• Structural
• Adapter
• Composite
• Decorator
• Behavioral
• Observer
• Strategy
• Template Method

23. Factory Method
“Define an interface for creating an object, but let
subclasses decide which class to instantance.
Factory Method lets a class defer instantiation to
subclasses.”

25. Demo

26. Abstract Factory
• It isolates concrete classes.
• It makes exchanging product famillies easy.
• It promotes consistency among products.
• Supporting new kinds of products is difficult.

27. Factory Method
• Provides hooks for subclasses.
• Connects parallel class hierarchies.

28. “Famous” Patterns
• Creational
• Abstract Factory
• Factory Method
• Structural
• Adapter
• Composite
• Decorator
• Behavioral
• Observer
• Strategy
• Template Method

29. Adapter
“Convert the interface of a class into another
interface clients expect. Adapter lets classes work
together that couldn’t otherwise because of
incompatible interfaces.”

31. Demo

32. Adapter
• How much adapting does Adapter do ?
• Pluggable adapters.
• Using two-way adapters to provide transparent.

33. “Famous” Patterns
• Creational
• Abstract Factory
• Factory Method
• Structural
• Adapter
• Composite
• Decorator
• Behavioral
• Observer
• Strategy
• Template Method

34. Composite
“Compose objects into tree structures to represent
part-whole hierarchies. Composite lets clients treat
individual objects and compositions of objects
uniformly.”

36. Demo

37. Composite
• Defines class hierarchies consisting of primitive
objects and composite objects.
• Make the client simple.
• Make it easier to add new kinds of components.
• Can make your design overly general.

38. “Famous” Patterns
• Creational
• Abstract Factory
• Factory Method
• Structural
• Adapter
• Composite
• Decorator
• Behavioral Pattern
• Observer
• Strategy
• Template Method

39. Decorator
“Attach additional responsibilities to an object
dynamically. Decorators provide a flexible
alternative to subclassing for extending
functionality.”

41. Demo

42. Decorator
• More flexibility than static inheritance.
• Avoids feature-laden classes high up in the
hierarchy.
• A decorator and it’s component aren’t critical.
• Lost of little objects.

43. “Famous” Patterns
• Creational
• Abstract Factory
• Factory Method
• Structural
• Adapter
• Composite
• Decorator
• Behavioral
• Observer
• Strategy
• Template Method

44. Observer
“Define a one-to-many dependency between
objects so that when one object changes state, all
its dependents are notified and updated
automatically.”

46. Demo

47. Observer
• Abstract coupling between Subject and
Observer.
• Support for broadcast communication.
• Unexpected updates.
• Lost of little objects.

48. “Famous” Patterns
• Creational
• Abstract Factory
• Factory Method
• Structural
• Adapter
• Composite
• Decorator
• Behavioral
• Observer
• Strategy
• Template Method

49. Strategy
“Define a family of algorithms, encapsulate each
one, and make them interchangeable. Strategy
lets the algorithm vary independently from clients
that use it.”

51. Demo

52. Strategy
• Families of related algorithms.
• An alternative to subclassing.
• Strategies eliminates conditional statements.
• Clients must be aware of different Strategies.
• Communication overhead between Strategy and
Context.
• Increased number of objects.

53. “Famous” Patterns
• Creational
• Abstract Factory
• Factory Method
• Structural
• Adapter
• Composite
• Decorator
• Behavioral
• Observer
• Strategy
• Template Method

54. Template Method
“Define the skeleton of an algorithm in an
operation, deferring some steps to subclasses.
Template Method lets subclasses redefine certain
steps of an algorithm without changing the
algorithm’s structure.”

56. Demo

57. Question and Answer

58. Conclusion

59. The gang of Four(GoF)
Raph Johnson, Erich Gamma,
Richard Helm, John Vlissides

61. tuan.do@axonactive.com
https://vn.linkedin.com/in/dominhtuan
Thank you !