This document discusses the SOLID principles of object-oriented design: Single Responsibility Principle, Open Closed Principle, Liskov Substitution Principle, Interface Segregation Principle, and Dependency Inversion Principle. It explains that SOLID is a collection of best practices that can be applied to design to achieve loose coupling and high maintainability. Each principle is then defined in one sentence and an example demo is provided to illustrate applying that principle.

1. SOLID Software Development
Ken Burkhardt

3. What is SOLID?
Single Responsibility Principle
Open Closed Principle
Liskov Substitution Principle
Interface Segregation Principle
Dependency Inversion Principle

4. Why SOLID?
S.O.L.I.D. is a collection of best-
practice, object-oriented design
principles which can be applied to
your design, allowing you to
accomplish various desirable goals
such as loose-coupling, higher
maintainability

5. Single Responsibility Principle
THERE SHOULD NEVER BE MORE
THAN ONE REASON FOR A CLASS TO
CHANGE.

7. Demo - Superclass

8. Open Closed Principle
SOFTWARE ENTITIES SHOULD BE
OPEN FOR EXTENSION BUT CLOSED
FOR MODIFICATION

10. Demo – Add New Validator

11. Liskov Substitution Principle
You should be able to use any derived
class in place of a parent class and have
it behave in the same manner without
modification. It ensures that a derived
class does not affect the behavior of the
parent class, i.e. that a derived class
must be substitutable for its base class.

13. Interface Segregation Principle
CLIENTS SHOULD NOT BE FORCED TO
DEPEND UPON INTERFACES THAT
THEY DO NOT USE

15. Demo - Animals

16. Dependency Inversion Principle
A. HIGH LEVEL MODULES SHOULD NOT
DEPEND UPON LOW LEVEL MODULES.
BOTH SHOULD DEPEND UPON
ABSTRACTIONS
B. ABSTRACTIONS SHOULD NOT DEPEND
UPON DETAILS. DETAILS SHOULD DEPEND
UPON ABSTRACTIONS

18. Bad designs and poor code is not good
because it's hard to change. Bad designs are:
- Rigid (change affects too many parts of
the system)
- Fragile (every change breaks something
unexpected)
- Immobile (impossible to reuse)

19. Demo - Interfaces