OO Design

SOLID is an acronym for the first five object-oriented design (OOD) and it stands for:

S - Single-responsiblity Principle O - Open-closed Principle L - Liskov Substitution Principle I - Interface Segregation Principle D - Dependency Inversion Principle

Single-responsiblity Principle

means that the class must have only one job

Open-closed Principle

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

Liskov Substitution Principle

Let q(x) be a property provable about objects of x of type T. Then q(y) should be provable for objects y of type S where S is a subtype of T. link

This means that every subclass or derived class should be substitutable for their base or parent class.

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. link

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. link