The [SOLID principles](http://wikipedia.org/en/SOLID_principles) are a set of five design guidelines intended to improve software readability, extensibility, and maintainability by promoting better software design practices. These principles were introduced by [[Robert C. Martin]] (Uncle Bob) in his 2000 paper "Design Principles and Design Patterns." These principles are widely accepted in object-oriented design and programming to make software systems more understandable, flexible, and maintainable. ### The Five SOLID Principles 1. **Single Responsibility Principle (SRP)** - **Definition**: A class should have only one reason to change, meaning it should have only one job or responsibility. - **Benefit**: SRP reduces the complexity of the class by limiting the impact of changes. When a class is focused on a single responsibility, it is less likely to be affected by changes in other parts of the system, leading to easier maintenance and fewer bugs. 2. **Open/Closed Principle (OCP)** - **Definition**: Software entities (classes, modules, functions, etc.) should be open for extension, but closed for modification. - **Benefit**: This principle encourages the extension of existing code by adding new functionality as new classes that inherit from existing ones or through interfaces, rather than altering existing code which can introduce new bugs in already tested code. 3. **[[Liskov Substitution Principle]] ([[LSP]])** - **Definition**: Objects of a superclass shall be replaceable with objects of its subclasses without requiring changes to the desirable properties of the program (correctness, task performed, etc.). - **Benefit**: LSP ensures that a subclass can stand in for its superclass without errors. If the principle is followed, it enhances the robustness of the system by enabling polymorphism and interchangability of classes. 4. **Interface Segregation Principle (ISP)** - **Definition**: Clients should not be forced to depend upon interfaces that they do not use. This principle is about business logic to client communication, and it advocates for creating specific interfaces for client specific behaviour, which opposes one general-purpose interface. - **Benefit**: ISP minimizes the impact of changes by reducing the dependencies of a class on unused methods. Smaller, specific interfaces are easier to implement, improving flexibility and the possibility of code reuse. 5. **Dependency Inversion Principle (DIP)** - **Definition**: High-level modules should not depend on low-level modules. Both should depend on abstractions (e.g., interfaces). Abstractions should not depend upon details. Details (concrete implementations) should depend upon abstractions. - **Benefit**: DIP reduces the direct dependency among different classes or modules. It enhances the system modularity and promotes the scalability and maintainability of the system by decoupling software components. ### Overall Importance The application of the [[SOLID principles]] can significantly enhance the quality and durability of software during development and ongoing maintenance. By adhering to these principles, developers can create systems that are easier to understand, change, and extend over time. These principles encourage a cleaner separation of concerns and more scalable architecture. As a result, software systems become more robust and less coupled, which significantly eases both the testing and the maintenance burdens. # References ```dataview Table title as Title, authors as Authors where contains(subject, "SOLID principles") or contains(subject, "SOLID") sort title, authors, modified, desc ```