How do you define a Single Responsibility?

Question

I know about \"class having a single reason to change\". Now, what is that exactly? Are there some smells/signs that could tell that class does not have a single responsibility?

Answer 1

The obvious sign is when your class ends up looking like a Big Ball of Mud, which is really the opposite of SRP (single responsibility principle).

Basically, all the object's services should be focused on carrying out a single responsibility, meaning every time your class changes and adds a service which does not respect that, you know you're "deviating" from the "right" path ;)

The cause is usually due to some quick fixes hastily added to the class to repair some defects. So the reason why you are changing the class is usually the best criteria to detect if you are about to break the SRP.