Software Architect's Handbook

Single Responsibility Principle (SRP)

The Single Responsibility Principle (SRP) states that each class should have only one responsibility, meaning it should do one thing and do that thing well. A responsibility is a reason to change, so each class should have only one reason to change. If we group together the functions that need to change for the same reason, and separate out the things that change for other reasons, we can create a class that follows this principle.

If a class has multiple responsibilities, there is a likelihood that it is used in a greater number of places. When one responsibility is changed, not only do we run a higher risk of introducing defects into other responsibilities in the same class, but there is a greater number ...