What is SOLID?

SOLID is an acronym that represents five design principles in object-oriented programming (OOP). These principles were introduced by Robert C. Martin and are widely accepted as best practices for creating maintainable and scalable software systems. Each letter in the acronym corresponds to one of the principles:

  1. Single Responsibility Principle (SRP): A class should have only one reason to change, meaning it should have a single responsibility. This principle encourages separating different responsibilities into individual classes, making them easier to understand, maintain, and modify.

  2. Open-Closed Principle (OCP): Software entities (classes, modules, functions, etc.) should be open for extension but closed for modification. This principle suggests designing systems in a way that allows new functionality to be added by extending existing code rather than modifying it, ensuring that existing code remains unchanged and reducing the risk of introducing bugs.

  3. Liskov Substitution Principle (LSP): Objects of a superclass should be replaceable with objects of its subclasses without affecting the correctness of the program. In other words, derived classes should be substitutable for their base classes without changing the behavior of the system. This principle ensures that inheritance hierarchies are well-defined and adhered to.

  4. Interface Segregation Principle (ISP): Clients should not be forced to depend on interfaces they do not use. This principle promotes designing fine-grained interfaces that are specific to the needs of the clients that use them, instead of creating large and general interfaces. By doing so, it prevents clients from being burdened with unnecessary dependencies.

  5. Dependency Inversion Principle (DIP): High-level modules should not depend on low-level modules. Both should depend on abstractions. This principle suggests that classes should depend on abstractions (interfaces or abstract classes) rather than concrete implementations. By doing so, it promotes loose coupling between components and allows for easier substitution of implementations.

The SOLID principles aim to improve the maintainability, reusability, and extensibility of software systems by guiding developers in creating well-structured and flexible code. They help promote modular design, separation of concerns, and the use of abstraction to achieve these goals.

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