Solid Principles

The SOLID principles are a set of design guidelines for writing maintainable and scalable software. These principles were first introduced by Robert C. Martin in the early 2000s, and they have since become a widely accepted approach to software design.

Single Responsibility Principle: A class should have one, and only one, reason to change. This principle states that a class should have a single, well-defined responsibility, and that this responsibility should be encapsulated within the class. An example of this would be a class that is responsible for handling user authentication. This class should only be responsible for authentication-related functionality and should not handle other responsibilities such as user data storage or user management.

Open-Closed Principle: A class should be open for extension but closed for modification. This principle states that a class should be designed in such a way that it can be extended to add new functionality without modifying the existing code. An example of this would be a class that is responsible for handling different types of payments. Instead of modifying the class to support new payment methods, new classes can be created that inherit from the payment class and add the necessary functionality.

Liskov Substitution Principle: Subtypes should be substitutable for their base types. This principle states that objects of a superclass should be able to be replaced with objects of a subclass without affecting the correctness of the program. An example of this would be a class that is responsible for handling different types of vehicles. The class for a car should be able to be replaced with the class for a truck without affecting the functionality of the program.

Interface Segregation Principle: A class should not be forced to implement interfaces it does not use. This principle states that a class should only be required to implement the interfaces that it needs to fulfill its responsibilities. An example of this would be a class that is responsible for handling user input. This class should only be required to implement the interface for handling user input and should not be forced to implement interfaces for other responsibilities such as user data storage.

Dependency Inversion Principle: High-level modules should not depend on low-level modules. Both should depend on abstractions. This principle states that high-level modules (such as the user interface) should not depend on low-level modules (such as the database) and that both should depend on abstractions (such as interfaces). An example of this would be a class that is responsible for displaying user data. This class should not depend on a specific database implementation and should instead depend on an interface for accessing user data.