SOLID

In object-oriented computer programming, SOLID is a mnemonic acronym for five design principles intended to make software designs more understandable, flexible and maintainable.

Principles

  • Single responsibility
  • Open–closed
  • Liskov substitution
  • Interface segregation
  • Dependency inversion
Snippet from Wikipedia: SOLID

In object-oriented computer programming, 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 American software engineer and instructor Robert C. Martin, first introduced in his 2000 paper Design Principles and Design Patterns.

The SOLID concepts are:

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

The SOLID acronym was introduced later in 2004 or thereabouts by Michael Feathers.

Although 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.