Unveiling SOLID Principles: Fundamentals of Modern Programming
Hello, everyone! In this article, I want to share some insights I've gained through courses and, especially, from reading Clean Code by Robert C. Martin, also known as "Uncle Bob." Among the book's many teachings, I find the SOLID principles to be one of the most important topics. Although widely discussed, it's easy to overlook or forget some of the details.
I faced this challenge myself, so I developed a method to remember and consistently apply these principles. To make it easier to understand, I used examples from our everyday lives, making these concepts more accessible. In this article, I’ll share these ideas with you.
Single Responsibility Principle
The Single Responsibility Principle states that a class should have only one responsibility. This means it should be designed to avoid breaking this principle during development. It might seem a bit abstract at first, so let’s break it down with a simple example.
Think of a mop and a broom. Each has a specific responsibility: a mop is made for mopping, and a broom is made for sweeping. Trying to sweep with a mop would violate the single responsibility principle.
Similarly, a class that performs multiple functions becomes harder to maintain and test. Changes in one responsibility can impact others, creating confusion and bugs. To put it simply, each class should focus on a single task, improving maintainability and readability.
Open-Closed Principle
The Open-Closed Principle says that a class should be open for extension (allowing new behaviors through inheritance) but closed for modification. In other words, once a class’s behaviors are defined, its code shouldn’t be altered.
Imagine you have a blueprint for a standard house, defining core structures like walls, roof, and windows. Now, you want to add a garage. Instead of modifying the original house blueprint, you could create a separate class for the garage that fits with the existing design.
This way, the house blueprint remains unchanged, but you can extend it with additions like a garage, garden, or pool without altering the core structure. This principle allows systems to evolve without modifying existing code, reducing risks and simplifying maintenance.
Liskov Substitution Principle
The Liskov Substitution Principle states that a subclass should be substitutable for its superclass without altering the program’s behavior. In other words, you should be able to use a derived class in place of the base class without issues.
Imagine you have a base class called Team with a method performTask(). Now, you have two subclasses: Developer and QA. The Developer class writes and tests code, while the QA class performs quality tests. If the system expects a Team member and you use a QA where a Developer was expected, problems may arise.
To solve this, ensure that both Developer and QA can perform appropriate tasks, so any Team member can be used without problems. This principle reminds us that subclasses should maintain the behavior of the superclass, ensuring consistency.
Interface Segregation Principle
The Interface Segregation Principle states that clients shouldn’t be forced to implement methods they don’t need. Imagine an interface called Accounts with methods for calculating property tax and vehicle tax. Now, suppose we have a class called Person implementing this interface. If this person only owns a car, implementing a method for property tax doesn’t make sense.
This principle encourages smaller, specific interfaces, so classes only implement what they need. This keeps code flexible and maintainable, avoiding unnecessary methods.
Dependency Inversion Principle
The Dependency Inversion Principle states that high-level modules (like business logic) shouldn’t directly depend on low-level modules (like database access), but rather on abstractions.
Think of an orchestra: the conductor (high-level module) leads the performance but doesn’t directly manage each instrument. The musicians (low-level modules) follow the conductor’s instructions through sheet music (abstractions). If the violinist is replaced with a cellist, the conductor’s role remains the same.
Similarly, in programming, high-level modules work with abstractions, allowing implementation details to change without disrupting the system.
Conclusion
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