This is one of my tutorials about Single Responsibility Principle and you can find its video course in below link :
https://www.aparat.com/v/Q7Anv
https://youtu.be/kBWhXsQ9Vqw
The single-responsibility principle (SRP) is a computer-programming principle that states that every module, class or function in a computer program should have responsibility over a single part of that program's functionality, and it should encapsulate that part. All of that module, class or function's services should be narrowly aligned with that responsibility. Robert C. Martin, the originator of the term, expresses the principle as, "A class should have only one reason to change," although, because of confusion around the word "reason" he also stated "This principle is about people.". In some of his talks, he also argues that the principle is, in particular, about roles or actors. For example, while they might be the same person, the role of an accountant is different from a database administrator. Hence, each module should be responsible for each role.
From wiki: https://en.wikipedia.org/wiki/Single-responsibility_principle