SOLID Principles

Introduction of SOLID Principles:

The SOLID Principles are sets of guidelines to help developers create software that is flexible, understandable and easy to maintain over time. The SOLID Principles have established their authority as definitive rules that all developers in the field should follow.

SOLID Principles is introduced by Robert C.Martin that represents five principles of object-oriented programming and design. These concepts ware later built upon by Michael Feathers, who introduce to the SOLID acronym.

Below is the five Solid Principle:

Single Responsibility Principle (SPR)

Open-Closed Principle (OCP)

Liskov Substitution Principle (LSP)

Interface Segregation Principle (ISP)

Dependency Inversion Principle (DIP)

These principles provide a way for developers to organize their code and create software that is flexible, easy to change, and testable. 

Single Responsibility Principle (SPR):

The Single Responsibility Principle states that a class should have only one reason to change, In other words, a class should have only one responsibility or job within the system like each object class (that is, specific method, variable, parameters etc.).

In this principle, we ensure that each class is focused and has a clear purpose, making it easier to understand, test, and maintain.

If a class has too many responsibilities, it can become hard to understand, maintain, and modify. By following SPR, we can create code that is more modular, easier to understand, and less prone to errors.

Imagine you have a class for managing the user authentication. Instead of also making it responsible for sending emails or other purpose you did keep those task separate. This make you code easier to understand.

Open-Closed Principle (OCP):

The Open/Closed Principle suggested that software entities (classes, modules, functions, etc.) should be open for extension but closed for modification. In simple terms, it means that we should be able to add new feature to a module without altering its source code.

"Open for extension" means we must design our module/class so that the new functionality can be added only when new requirements are generated.

"Closed for modification" means we have already developed a class, and it has gone through unit testing. We should then not alter it until we find bugs. As it says, a class should be open for extensions; we can use inheritance.

This principle helps us reduce the risk of introducing bugs and side effects when we modify existing code. By following the OCP, we can ensure that our software remains flexible and easier to maintain over time.

Liskov Substitution Principle (LSP):

The Liskov Substitution Principle You should be able to use any derived class instead of parent class and have it behave in the same way without modification.

It ensures that a derived class does not affect the behavior of the parent class; in other words, a derived class must be substitutable for its base class.

In other words, a derived class should behave like its base class in all contexts. In more simple terms, if class A is a subtype of class B, you should be able to replace B with A without breaking the behavior of your program.

Interface Segregation Principle (ISP):

The Interface Segregation Principle focuses on designing interfaces that are specific to their client's needs. It states that no client should be forced to depend on methods it does not use.

This principle suggests that Instead of creating large interfaces that covers all the possible methods, its batter to create smaller, more focused interface for specific use cases.

For instance, let's imagine a scenario where we have a printer interface intended to be implemented by various types of printers. According to ISP, instead of having one large interface containing methods for printing, scanning, faxing, and photocopying, it's preferable to break it down into smaller, more specialized interfaces. We could have separate interfaces for printing, scanning, and so on. This way, a client that only requires printing functionality.

Dependency Inversion Principle (DIP):

The Dependency Inversion Principle suggested that high-level modules should not depend on low-level modules. Instead, both should depend on abstractions.

High-level modules/classes implement business rules or logic in a system (application). Low-level modules/classes deal with more detailed operations; in other words, they may write information to databases or pass messages to the operating system or services.

Abstractions should not depend on details; rather, details should depend on abstractions. By separating high-level modules from the specifics of their implementations, we can promote flexibility, reusability, and easier testing.

Conclusion:

In this article, you learned about the SOLID principles which are a very important part of general Design Principles.

By applying these principles in your software development projects, you can create code that is easier to maintain, extend, and modify. This will also lead to better collaboration among team members, as the code becomes more modular and easier to work with.