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Single Responsibility Principle

A software module has one, and only one, reason to change.

Robert C. Martin

This principle states that a module, which could be a class, a function, a package or even a variable, has only one reason to change.1

When you are working in a class or a function you need to think about what is that function is trying to achieve, is a function is working on calculating the total amount of an order, it should not worry about opening or closing databases, or network requests, those should be handle by another "module".

SRP helps us to avoid coupling meaning that a particular piece of code is bound to another piece, by working with SRP in mind it will create modules that are decoupled by design.

  1. Robert C. Martin. Clean Architecture, First Edition, Prentice Hall, 2017, p. 58-59↩