Why You Need SOLID as a Developer

Do You Need SOLID to Be a Better Developer? You don’t need SOLID to write working code—many developers manage without it. But to become a better developer (and potentially earn more by writing high-quality, maintainable software), learning SOLID basics is a smart move. SOLID’s five principles make code more understandable, flexible, and maintainable. 1. Single Responsibility Principle "Do one thing and do it well"—that’s Uncle Bob’s advice from his book. SRP means a class should have just one responsibility. SRP Failing The Book class has two responsibilities: Managing book details (title, author, description)—its core purpose. Interacting with a database (saveToDatabase)—unrelated to the book’s properties. That’s a mistake. SRP Essence To fix this, separate the responsibilities: Book focuses solely on book-related tasks. DatabaseManager handles database operations. Each class now has one reason to change: Book if book properties change. DatabaseManager if database logic changes. 2. Open/Closed Principle The Open/Closed Principle (OCP) means software entities (classes, modules) should be open for extension but closed for modification—add new functionality without altering existing code. OCP Failing The ShippingCalculator calculates shipping costs based on book type. The mistake? Adding a new type requires modifying it with another elseif, breaking OCP. This opens the class to changes, risking bugs. OCP Essence The ShippingCalculator stays closed for modification by using a ShippingType interface. New types (PaperbackShipping, HardcoverShipping) extend it, delegating logic to specific classes. This keeps the system flexible and bug-free. 3. Liskov Substitution Principle The Liskov Substitution Principle (LSP) states that subclass objects should replace parent class objects without breaking the program—substitution should work seamlessly. LSP Failing A Bird class assumes all birds can fly(), but a Penguin subclass can’t. This breaks LSP because Penguin isn’t substitutable for Bird without altering behavior. LSP Essence An Animal interface with a move() method lets Sparrow and Penguin implement it their way. The makeAnimalMove() function works with any Animal subclass without breaking, satisfying LSP. 4. Interface Segregation Principle ISP states that classes shouldn’t be forced to implement interfaces they don’t use—keep interfaces small and specific. ISP Failing A Worker interface includes work() and manage(). Developer only needs work() but must implement manage() too, breaking ISP by forcing unused methods. ISP Essence Workable and Manageable are separate interfaces. Developer implements only Workable; Manager implements both. No unused methods are forced, satisfying ISP. 5. Dependency Inversion Principle DIP states that high-level modules shouldn’t depend on low-level ones—both should rely on abstractions (interfaces) for flexibility. DIP Failing Notification (high-level) directly depends on FileLogger (low-level). Switching to DatabaseLogger requires changing Notification, breaking DIP due to tight coupling. DIP Essence A Logger interface defines the contract. Notification depends on Logger, not FileLogger. Swapping FileLogger for DatabaseLogger needs no changes to Notification, following DIP by relying on abstractions. Final Thoughts SOLID principles improve code quality and flexibility. Apply them to level up your skills and projects. Thanks for reading!

Mar 9, 2025 - 03:53

Do You Need SOLID to Be a Better Developer?

You don’t need SOLID to write working code—many developers manage without it. But to become a better developer (and potentially earn more by writing high-quality, maintainable software), learning SOLID basics is a smart move. SOLID’s five principles make code more understandable, flexible, and maintainable.

1. Single Responsibility Principle

"Do one thing and do it well"—that’s Uncle Bob’s advice from his book. SRP means a class should have just one responsibility.

SRP Failing

The Book class has two responsibilities:

Managing book details (title, author, description)—its core purpose.
Interacting with a database (saveToDatabase)—unrelated to the book’s properties. That’s a mistake.

SRP Essence

To fix this, separate the responsibilities:

Book focuses solely on book-related tasks.
DatabaseManager handles database operations. Each class now has one reason to change:
Book if book properties change.
DatabaseManager if database logic changes.

2. Open/Closed Principle

The Open/Closed Principle (OCP) means software entities (classes, modules) should be open for extension but closed for modification—add new functionality without altering existing code.

OCP Failing

The ShippingCalculator calculates shipping costs based on book type.
The mistake?
Adding a new type requires modifying it with another elseif, breaking OCP. This opens the class to changes, risking bugs.

OCP Essence

The ShippingCalculator stays closed for modification by using a ShippingType interface. New types (PaperbackShipping, HardcoverShipping) extend it, delegating logic to specific classes. This keeps the system flexible and bug-free.

3. Liskov Substitution Principle

The Liskov Substitution Principle (LSP) states that subclass objects should replace parent class objects without breaking the program—substitution should work seamlessly.

LSP Failing

A Bird class assumes all birds can fly(), but a Penguin subclass can’t. This breaks LSP because Penguin isn’t substitutable for Bird without altering behavior.

LSP Essence

An Animal interface with a move() method lets Sparrow and Penguin implement it their way. The makeAnimalMove() function works with any Animal subclass without breaking, satisfying LSP.

4. Interface Segregation Principle

ISP states that classes shouldn’t be forced to implement interfaces they don’t use—keep interfaces small and specific.

ISP Failing

A Worker interface includes work() and manage(). Developer only needs work() but must implement manage() too, breaking ISP by forcing unused methods.

ISP Essence

Workable and Manageable are separate interfaces. Developer implements only Workable; Manager implements both. No unused methods are forced, satisfying ISP.

5. Dependency Inversion Principle

DIP states that high-level modules shouldn’t depend on low-level ones—both should rely on abstractions (interfaces) for flexibility.

DIP Failing

Notification (high-level) directly depends on FileLogger (low-level). Switching to DatabaseLogger requires changing Notification, breaking DIP due to tight coupling.

DIP Essence

A Logger interface defines the contract. Notification depends on Logger, not FileLogger. Swapping FileLogger for DatabaseLogger needs no changes to Notification, following DIP by relying on abstractions.

Final Thoughts

SOLID principles improve code quality and flexibility. Apply them to level up your skills and projects. Thanks for reading!