Solid Design

not liquid

• s: Single Responsibility Principle

  • Each class should have only one sole purpose, and not be filled with excessive functionality

  • ex : loan class, there can be multiple loans, car, personal, home.

  • ex : send otp class, there can be multiple ways to send otp, email, sms, whatsapp.

• o: Open & Close Principle

  • Classes should be open for extension, closed for modification.

  • In other words, you should not have to rewrite an existing class for implementing new features.

  • ex: using interfaces, can can implement create new class to implement new features.

• l: Leskov's Subsititution Principle

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

  • ex: we have 3 social media: facebook, instagram & whatsapp

    • whatsapp doesnt support features like publish posts

    • there is no calling on instagram

  • we create interface that contain common functionality, have our classes extend from them

  • for specific features, we create new interfaces for them

• i: Interfae Segragation Principle

  • Interfaces should not force classes to implement what they can’t do.

  • Large interfaces should be divided into small ones.

• d: Dependency Inversion Principle

  • The principle states that we must use abstraction (abstract classes and interfaces) instead of concrete implementation.

  • High level modules should not depend on the low level module but both should depend on the abstraction.

  • ex: when perform payment, it doesnt matter whether you visa or mastercard, debit or credit card, payment provider will take it.

  • instead of taking input a specific class, take a interface which can be implemented by classes

For examples with code : https://medium.com/@javatechie/solid-design-principle-java-ae96a48db97