SOLID: The First 5 Principles of Object Oriented Design Part 1

The SOLID Principles are five principles of Object-Oriented class design. They are a set of rules and best practices to follow while designing a class structure.

Solid principles are a crucial aspect of software development that ensures software systems are scalable, maintainable, and robust. SOLID is an acronym for five design principles that help achieve this objective:

• Single Responsibility Principle (SRP)
• Open-Closed Principle (OCP)
• Liskov Substitution Principle (LSP)
• Interface Segregation Principle (ISP)
• Dependency Inversion Principle (DIP)

These principles emphasize different aspects of software design that work together to create a strong foundation for developing well-architected systems.

In this article, we will discuss to each principle individually.

The Single Responsibility Principle(SRP)

The Single Responsibility Principle states that a class should have only one reason to change, meaning it should have a single responsibility or a single job to do. This means that a class should be focused on one area of functionality, and it should not be responsible for any unrelated tasks. This principle aims to make code easier to understand, modify, and maintain by ensuring that each class is focused on a particular area of functionality and is not responsible for unrelated tasks.

In practice, SRP means that a class should have only one reason to change. For example, if you have a class that is responsible for both storing data in a database and rendering HTML, it violates the SRP principle because if either the database structure or the HTML rendering logic changes, the class would need to be modified.

Here's an example of a class that violates the SRP principle:

To apply the SRP principle to this class, we can split it into two classes, each with its own responsibility:

In this refactored code, the Post class is responsible for storing post data in the database, and the PostRenderer class is responsible for rendering the HTML for the post. Each class has only one responsibility and only one reason to change.

Here's an example of how you might use the PostRenderer class in Laravel:

In this example, the PostController is responsible for handling HTTP requests and using the PostRenderer to render the user profile HTML. The PostRenderer class can be easily reused in other parts of the application where post rendering is required.

By adhering to SRP, we can ensure that each class has a clear and focused purpose, making it easier to reason about and change. This can also help to reduce code duplication and improve code reuse, as classes can be designed to perform specific tasks that can be used across the application.

In summary, SRP is essential in SOLID because it helps to create more maintainable and extensible software by promoting the creation of focused, understandable, and testable classes.

Stay tuned for the next part of this article.