Read: 08 - OO Design

SOLID: The First 5 Principles of Object Oriented Design

- S - Single-responsiblity Principle.

Class should have only one job.

- O - Open-closed Principle.

Objects or entities should be open for extension but closed for modification.

- L - Liskov Substitution Principle.

Every subclass or derived class should be substitutable for their base or parent class.

- I - Interface Segregation Principle.

A client should never be forced to implement an interface that it doesn’t use, or clients shouldn’t be forced to depend on methods they do not use.

- D - Dependency Inversion Principle

Entities must depend on abstractions, not on concretions. It states that the high-level module must not depend on the low-level module, but they should depend on abstractions.