The SOLID principles are a set of five design principles in object-oriented programming that help to create software that is easy to maintain, understand, and extend.
The SOLID principles are particularly helpful when working with complex software systems and can improve code quality and reduce the risk of introducing bugs.
Each letter in SOLID stands for one of the five principles:
S – Single Responsibility Principle (SRP)
O – Open/Closed Principle (OCP)
L – Liskov Substitution Principle (LSP)
I – Interface Segregation Principle (ISP)
D – Dependency Inversion Principle (DIP)
1. Single Responsibility Principle (SRP)
Definition: A class should have only one reason to change, meaning it should have only one responsibility. If a class has more than one responsibility, it becomes harder to maintain and modify, and it can introduce unwanted side effects when one responsibility changes.
2. Open/Closed Principle (OCP)
Definition: Software entities (classes, modules, functions, etc.) should be open for extension but closed for modification. This means you should be able to add new functionality to a class without modifying its existing code.
3. Liskov Substitution Principle (LSP)
Definition: Objects of a superclass should be replaceable with objects of a subclass without affecting the correctness of the program. In other words, derived classes must be substitutable for their base classes.
4. Interface Segregation Principle (ISP)
Definition: A client should not be forced to implement interfaces it doesn't use. This principle is about splitting large, complex interfaces into smaller, more specific ones. It helps avoid “fat” interfaces that force classes to implement unnecessary methods.
5. Dependency Inversion Principle (DIP)
Definition: High-level modules should not depend on low-level modules. Both should depend on abstractions. Additionally, abstractions should not depend on details. Details should depend on abstractions. This principle helps to decouple classes and makes the system more flexible and easier to maintain.
Summary of SOLID Principles:
Principle | Description |
S – Single Responsibility Principle (SRP) | A class should have only one reason to change, i.e., one responsibility. |
O – Open/Closed Principle (OCP) | A class should be open for extension but closed for modification. |
L – Liskov Substitution Principle (LSP) | Objects of a superclass should be replaceable with objects of a subclass. |
I – Interface Segregation Principle (ISP) | Clients should not be forced to implement methods they don't use. |
D – Dependency Inversion Principle (DIP) | High-level modules should not depend on low-level modules; both should depend on abstractions. |
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