SOLID Fundamentals

Super quick introduction to the five basic principles of object-oriented design known by the acronymn SOLID.

Slide from the 2nd florida coders user group meeting. 2014/01/08

Transcript

1. SOLID Fundamentals @mcminton
2. Before we begin…
3. Before we begin… a short note on programming
4. Programming has more in common with painting or composing than with the discipline of engineering
5. It absolutely is NOT a repeatable science
6. It absolutely is NOT a repeatable science There is no answer that’s correct 100% of the time
7. Having said that
8. Mankind has collected decades of valuable experience in what works well and what doesn't
9. This experience can be formalized as Design Patterns Principles
10. Think of these are guidelines for solving problems that seem to recur in programming
11. SOLID
12. SOLID a cute acronym for 5 basic principles for doing object-oriented right 5
13. S - Single Responsibility O - Open/Closed L - Liskov Substituion I - Interface Segregation D - Dependency Inversion
14. Single Responsibility
15. Single Responsibility a class should have only a single responsibility.
16. Single Responsibility a class should have only a single responsibility. Super simple to understand
17. Single Responsibility a class should have only a single responsibility. Super simple to understand Hard to get right
18. Single Responsibility a class should have only a single responsibility. Super simple to understand Hard to get right Avoid God classes
19. Single Responsibility a class should have only a single responsibility. Super simple to understand Hard to get right Avoid God classes Many smaller classes
20. Open/Closed
21. Open/Closed software entities should be open to extension, but closed to modification
22. Open/Closed software entities should be open to extension, but closed to modification Think virtual & overrides
23. Open/Closed software entities should be open to extension, but closed to modification Think virtual & overrides Don’t change your body just to change your clothes
24. Open/Closed software entities should be open to extension, but closed to modification Think virtual & overrides Don’t change your body just to change your clothes Avoid switch on types
25. Liskov Substitution
26. Liskov Substitution objects in a program should be replaceable with instances of their subtypes without altering the correctness of that program
27. Liskov Substitution objects in a program should be replaceable with instances of their subtypes without altering the correctness of that program demo time
28. Interface Segregation
29. Interface Segregation many client-specific interfaces are better than one general-purpose interface
30. Interface Segregation many client-specific interfaces are better than one general-purpose interface Similar to SRP
31. Interface Segregation many client-specific interfaces are better than one general-purpose interface Similar to SRP Don’t be afraid of interfaces
32. Interface Segregation many client-specific interfaces are better than one general-purpose interface Similar to SRP Don’t be afraid of interfaces Don’t force unnecessary methods
33. Dependency Inversion
34. Dependency Inversion one should “Depend upon Abstractions. Do not depend upon concretions.”
35. Dependency Inversion one should “Depend upon Abstractions. Do not depend upon concretions.” demo time
36. more reading @mcminton C# in Depth by Jon Skeet http://en.wikipedia.org/wiki/SOLID_(object-oriented_design)