Single Responsibility Principle

The Single Responsibility Principle (SRP) is a principle of object-oriented programming that states that every class should have a single responsibility, and that responsibility should be entirely encapsulated by the class.

This means that a class should have only one reason to change, and that any changes to the class should be made in service of that one responsibility.

Here is an example of a class that does not follow the Single Responsibility Principle:

In this example, the User class has three responsibilities: storing user information, authenticating users, and sending emails. So, it would be better to encapsulate them in separate classes to avoid several potential problems. These problems include:

• The class becoming large and unwieldy, which can make it difficult to understand and maintain.
• The class being more prone to errors, as changes to the class to support one responsibility may unintentionally break code related to another responsibility.
• The overall design of the program becoming more complex, as it would require more coordination between the User class and other parts of the program.
• The class being difficult to reuse in other parts of the program, due to its diverse set of responsibilities.

By encapsulating the responsibilities of the User class in separate classes, we can avoid these problems and create a more modular, maintainable, and scalable design.

Here is how we could refactor this code to follow the Single Responsibility Principle:

In this revised design, each class has a single responsibility:

• The User class is responsible for storing user information.
• The Authentication class is responsible for authenticating users.
• The Emailer class is responsible for sending emails.

This design follows the Single Responsibility Principle, because each class has a single, well-defined responsibility and any changes to the class should be made in service of that responsibility.