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Britt Ballard

September 3, 2014 updated on November 1, 2016

• web
• ios
• back to basics
• good code
• ruby
• swift

SOLID is an acronym created by Bob Martin and Michael Feathers that refers to five fundamental principles that help engineers write maintainable code. We like to think of these principles as the foundational elements we use when evaluating the health of our codebase and architectural approach. The principles that make up the acronym are as follows:

• S - Single Responsibility Principle
• O - Open/Closed Principle
• L - Liskov Substitution Principle
• I - Interface Segregation Principle
• D - Dependency Inversion Principle

Let’s take a closer look at each of these principles with some examples.

Single Responsibility Principle

The Single Responsibility Principle is the most abstract of the bunch. It helps keep classes and methods small and maintainable. In addition to keeping classes small and focused it also makes them easier to understand.