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What is SOLID: The basic principles of object-oriented programming

SOLID is a set of five principles that help developers create more supported and scalable systems based on object—oriented programming (OOP). These principles were popularized by Robert Martin, known as Uncle Bob, and became the basis for the development of high-quality software. Let's look at each of these principles.

The principle of sole responsibility states that a class should have only one reason to change. In other words, each class should be engaged in only one task. This helps to avoid "bloating" classes when one class tries to do too much. This approach makes it easier to test and maintain the code.

Example: If you have a class that handles both user data and database logic, it is better to divide these tasks into two separate classes.

According to this principle, software entities (classes, modules, functions) should be open for expansion, but closed for modification. This means that you can add new functionality without changing existing code. This approach helps to prevent errors and makes the code more flexible.

Example: if you need to add new functionality, it is better to create a new class or method rather than modify existing code.

The Liskov substitution principle states that objects of a child class should be interchangeable with objects of the parent class without violating the logic of the program. This ensures that using inheritance does not lead to unexpected errors.

Example: if you have a class "Bird" and a child class "Penguin", "Penguin" should be able to perform all the actions that "Bird" can perform, but the implementation of these actions may differ.

The principle of interface separation suggests that it is better to have several highly specialized interfaces than one common one that includes many methods. This prevents the creation of "heavy" interfaces and allows classes to implement only those methods that they really need.

Example: if the "Animal" interface includes the "fly", "swim" and "walk" methods, and your "Fish" class can only swim, it is better to create separate interfaces for each action.

The dependency inversion principle assumes that high-level modules should not depend on low-level modules. Both types of modules should depend on abstractions. This helps to reduce the dependency between system components and improves the modularity of the code.

Example: instead of the Report class being directly dependent on the Database class, it is better to create a Storage interface that will be implemented by both the Database class and other possible data sources.

Applying SOLID principles helps developers create more structured, maintainable, and flexible code. These principles are especially useful in the development of large systems, where it is important to avoid errors and difficulties in maintaining the code. By following SOLID, you can improve the quality of your software and make it more resilient to changes in the future.

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Aug. 15, 2024 04:56