2. SOLID
Clean code for
mere mortals

5. { What is software development?
‹ Software development is not (only)
programming
‹ Agile Software Development:
Principles, Patterns, and Practices
‹ The Pragmatic Programmer
‹ Manifesto for Software Craftsmanship

6. { Software requirements
‹ Notoriously fluid
‹ Changes in scope
‹ Changes in functionalities
‹ Changes in environments
‹ The only constant is change
‹ We should embrace change!

7. { Software Rot
‹ Occurs to any software that survives the
first version
‹ Rigidity
‹ Fragility
‹ Immobility
‹ Viscosity

8. { SOLID Principles
‹ Introduced by Robert C. Martin
(Uncle Bob)
‹ An acronym of acronyms
‹ Not a piece of code
‹ Tool for “code smell” detection

9. { SOLID Principles
‹ Single Responsibility Principle
‹ Open Closed Principle
‹ Liskov Substitution Principle
‹ Interface Segregation Principle
‹ Dependency Inversion Principle

10. { SOLID
‹ Single Responsibility Principle
‹ Single Level of abstraction
‹ Just one reason to change
‹ Antithesis of the “God” object

11. SRP IN ACTION

12. { SOLID
‹ Open Closed Principle
‹ Inspired from work on Eiffel
‹ Open for extensions
‹ Closed for modification
‹ Use polymorphic behaviours

13. OCP IN ACTION

14. { SOLID
‹ Liskov Substitution Principle
‹ Named after Barbara Liskov
‹ Subclasses should be substitutable
for their base classes.
‹ Design by Contract
‹ A Circle is not an Ellipse

15. LSP IN ACTION

16. { SOLID
‹ Interface Segregation Principle
‹ It’s not always about the `interface`
keyword
‹ An interface should have a single
purpose
‹ An interface should define a client

17. ISP IN ACTION

18. { SOLID
‹ Dependency Inversion
‹ Depend upon abstractions.
‹ Do not depend upon concretions.
‹ Object creation problems – use
object factories.
‹ The principle behind Inversion-of-
control and Dependency Injection

19. DIP IN ACTION

20. { Bonus Principle: YAGNI
‹ You Ain’t Gonna Need It
‹ Just-in-time implementation
‹ Avoid architecture astronauts
‹ Simpler code is easier to refactor
‹ Keep it as simple as possible, but
not simpler

21. Questions?
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