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SOLID (object-oriented design)

In object-oriented computer programming, the term SOLID is a mnemonic acronym for five design principles intended to make software designs more understandable, flexible and maintainable. The principles are a subset of many principles promoted by Robert C. Martin.[1][2][3] Though they apply to any object-oriented design, the SOLID principles can also form a core philosophy for methodologies such as agile development or adaptive software development.[3] The SOLID acronym was introduced by Michael Feathers.


Single responsibility principle[4]
a class should have only a single responsibility (i.e. changes to only one part of the software's specification should be able to affect the specification of the class).
Open/closed principle[5]
"software entities … should be open for extension, but closed for modification."
Liskov substitution principle[6]
"objects in a program should be replaceable with instances of their subtypes without altering the correctness of that program." See also design by contract.
Interface segregation principle[7]
"many client-specific interfaces are better than one general-purpose interface."[8]
Dependency inversion principle[9]
one should "depend upon abstractions, [not] concretions."[8]

See alsoEdit


  1. ^ Robert C. Martin. "Principles Of OOD". Retrieved 2014-07-17. . (Note the reference to “the first five principles”, though the acronym is not used in this article.) Dates back to at least 2003.
  2. ^ Robert C. Martin. "Getting a SOLID start". Retrieved 2013-08-19. 
  3. ^ a b Sandi Metz (May 2009). "SOLID Object-Oriented Design". Retrieved 2009-01-15.  Talk given at the 2009 Gotham Ruby Conference.
  4. ^ "Single Responsibility Principle" (PDF). Archived from the original (PDF) on 1 June 2015. 
  5. ^ "Open/Closed Principle" (PDF). Archived from the original (PDF) on 5 September 2015. 
  6. ^ "Liskov Substitution Principle" (PDF). Archived from the original (PDF) on 5 September 2015. 
  7. ^ "Interface Segregation Principle" (PDF). 1996. Archived from the original (PDF) on 5 September 2015. 
  8. ^ a b Robert C. Martin (2000), "Design Principles and Design Patterns" (PDF),, archived from the original (PDF) on 6 September 2015, retrieved 2009-01-14 
  9. ^ "Dependency Inversion Principle" (PDF). Archived from the original (PDF) on 5 September 2015.