SOLID Principles
Robert C. Martin introduced these concepts in his 2000 paper “Design Principles and Design Patterns” to help developers write software that is easy to understand, modify, and extend. The principles aim to make software development more efficient and effective.
Michael Feathers later built upon these concepts and introduced us to the SOLID acronym.
The SOLID acronym stands for:
- Single Responsibility Principle (SRP)
- Open-Closed Principle (OCP)
- Liskov Substitution Principle (LSP)
- Interface Segregation Principle (ISP)
- Dependency Inversion Principle (DIP)
Developers can use these principles to organise their code and create flexible, easy-to-change, and testable software. Applying SOLID principles can result in code that is more modular, maintainable, and extensible. It can also make it easier for developers to collaborate on a codebase.
- Single Responsibility Principle(SRP)
The Single Responsibility Principle (SRP) states that a class should have only one responsibility. This means that a class should have only one job to do, and it should do it well.
If a class has too many responsibilities, it can become hard to understand, maintain, and modify. Changes to one responsibility can inadvertently affect another responsibility, leading to unintended consequences and bugs.
2. Open-Closed Principle (OCP)
The Open-Closed Principle (OCP) states that software entities should be open for extension but closed for modification. This means that the behavior of a software entity can be extended without modifying its source code.
The OCP promotes software extensibility and maintainability. By allowing software entities to be extended without modification, developers can add new functionality without the risk of breaking existing code. This results in code that is easier to maintain, extend, and reuse.
3. Liskov Substitution Principle (LSP)
The Liskov Substitution Principle (LSP) states that a derived class should be able to replace its base class without affecting the correctness of the program.
This means that a derived class should behave like its base class in all contexts. In simpler terms, if class A is a subtype of class B, you should be able to replace B with A without breaking the behavior of your program.
The LSP is important because it ensures that a program’s behavior remains consistent and predictable when substituting objects of different classes. Violating the LSP can cause unexpected behavior, bugs, and maintainability issues.
4. Interface Segregation Principle (ISP)
The Interface Segregation Principle (ISP) focuses on designing interfaces that meet the specific needs of their clients. It states that clients should not be required to depend on methods they do not use.
The principle suggests creating smaller, more focused interfaces for specific use cases instead of a large interface that covers all possible methods. This approach results in more cohesive and less coupled interfaces.
5. Dependency Inversion Principle (DIP)
The Dependency Inversion Principle (DIP) states that high-level modules should not depend on low-level modules, but both should depend on abstractions. Abstractions should not depend on details — details should depend on abstractions.
This principle aims to reduce coupling between modules, increase modularity, and make the code easier to maintain, test, and extend.
This article introduces the SOLID principles, which are essential design principles for software development.
By applying these principles, you can create code that is easier to maintain, extend, and modify. This leads to more robust, flexible, and reusable software, as well as better collaboration among team members. The principles help to make the code more modular and easier to work with.
