SOLID Principles

A basic tool or technique that when applied to designing or writing code makes that code more flexible, maintainable or extensible

• Single responsibility principle
• Open/closed principle
• Liskov substitution principle
• Interface segregation principle
• Dependency inversion principle

The SRP states that every object should have a single responsibility and all of the object's methods are focussed on carrying out that responsibility

Classes should be open to extension and closed to modification

When code makes decisions depending on type

• 1. High level modules should not depend on low level modules. Both should depend on abstractions.
• 1. Abstractions should not depend on details. Details should depend on abstractions.

Subtypes must be substitutable for their based types

When you want to use another class's functionality, but don't want to change the functionality

• Delegation
• Composition
• Aggregation

No client should be forced to depend on methods that it does not use