S.O.L.I.D: The First 5 Principles of Object Oriented Design

S.O.L.I.D is an acronym for the first five object-oriented design(OOD)** principles** by Robert C. Martin, popularly known as Uncle Bob.

These principles, when combined together, make it easy for a programmer to develop software that are easy to maintain and extend. They also make it easy for developers to avoid code smells, easily refactor code, and are also a part of the agile or adaptive software development.

• S - Single-responsiblity principle
• O - Open-closed principle
• L - Liskov substitution principle
• I - Interface segregation principle
• D - Dependency Inversion Principle

Single-responsibility Principle

A class should have one and only one reason to change, meaning that a class should 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.

All this is stating is that every subclass/derived class should be substitutable for their base/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.

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.

Honestly, S.O.L.I.D might seem to be a handful at first, but with continuous usage and adherence to its guidelines, it becomes a part of you and your code which can easily be extended, modified, tested, and refactored without any problems.

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