SOLID
| SOLID |
|---|
| Principles |
In software programming, SOLID is a mnemonic acronym for five design principles intended to make object-oriented designs more understandable, flexible, and maintainable. Although the SOLID principles apply to any object-oriented design, they can also form a core philosophy for methodologies such as agile development or adaptive software development.[1]
Software engineer and instructor Robert C. Martin[2][3][1] introduced the basic principles of SOLID design in his 2000 paper Design Principles and Design Patterns about software rot.[3][4]: 2–3 The SOLID acronym was coined around 2004 by Michael Feathers.[5]
Principles
[edit]Single responsibility principle
[edit]The single-responsibility principle (SRP) states that "there should never be more than one reason for a class to change."[6] In other words, every class should have only one responsibility.[7]
Importance
[edit]- Maintainability: When classes have a single, well-defined responsibility, they're easier to understand and modify.
- Testability: It's easier to write unit tests for classes with a single focus.
- Flexibility: Changes to one responsibility don't affect unrelated parts of the system.[7]
Open–closed principle
[edit]The open–closed principle (OCP) states that "software entities ... should be open for extension, but closed for modification."[8]
Importance
[edit]- Extensibility: New features can be added without modifying existing code.
- Stability: Reduces the risk of introducing bugs when making changes.
- Flexibility: Adapts to changing requirements more easily.
Liskov substitution principle
[edit]The Liskov substitution principle (LSP) states that "functions that use pointers or references to base classes must be able to use objects of derived classes without knowing it."[9] [9]
Importance
[edit]- Polymorphism: Enables the use of polymorphic behavior, making code more flexible and reusable.
- Reliability: Ensures that subclasses adhere to the contract defined by the superclass.
- Predictability: Guarantees that replacing a superclass object with a subclass object won't break the program.[9]
Interface segregation principle
[edit]The interface segregation principle (ISP) states that "clients should not be forced to depend upon interfaces that they do not use."[10][4]
Importance
[edit]- Decoupling: Reduces dependencies between classes, making the code more modular and maintainable.
- Flexibility: Allows for more targeted implementations of interfaces.
- Avoids unnecessary dependencies: Clients don't have to depend on methods they don't use.
Dependency inversion principle
[edit]The dependency inversion principle (DIP) states to depend upon abstractions, [not] concretes.[11][4]
Importance
[edit]- Loose coupling: Reduces dependencies between modules, making the code more flexible and easier to test.
- Flexibility: Enables changes to implementations without affecting clients.
- Maintainability: Makes code easier to understand and modify.[11][4]
See also
[edit]- Code reuse
- GRASP (object-oriented design)
- Inheritance (object-oriented programming)
- List of software development philosophies
References
[edit]- ^ a b Metz, Sandi (May 2009). "SOLID Object-Oriented Design". YouTube. Archived from the original on 2021-12-21. Retrieved 2019-08-13. Talk given at the 2009 Gotham Ruby Conference.
- ^ Martin, Robert C. "Principles Of OOD". ButUncleBob.com. Archived from the original on Sep 10, 2014. Retrieved 2014-07-17.. (Note the reference to "the first five principles", although the acronym is not used in this article.) Dates back to at least 2003.
- ^ a b Martin, Robert C. (13 Feb 2009). "Getting a SOLID start". Uncle Bob Consulting LLC (Google Sites). Archived from the original on Sep 17, 2013. Retrieved 2013-08-19.
- ^ a b c d Martin, Robert C. (2000). "Design Principles and Design Patterns" (PDF). objectmentor.com. Archived from the original on 2015-09-06.
- ^ Martin, Robert (2018). Clean Architecture: A Craftsman's Guide to Software Structure and Design. Pearson. p. 58. ISBN 978-0-13-449416-6.
- ^ "Single Responsibility Principle" (PDF). objectmentor.com. Archived from the original on 2 February 2015.
- ^ a b Martin, Robert C. (2003). Agile Software Development, Principles, Patterns, and Practices. Prentice Hall. p. 95. ISBN 978-0135974445.
- ^ "Open/Closed Principle" (PDF). objectmentor.com. Archived from the original on 5 September 2015.
- ^ a b c "Liskov Substitution Principle" (PDF). objectmentor.com. Archived from the original on 5 September 2015.
- ^ "Interface Segregation Principle" (PDF). objectmentor.com. 1996. Archived from the original on 5 September 2015.
- ^ a b "Dependency Inversion Principle" (PDF). objectmentor.com. Archived from the original on 5 September 2015.