Single Responsibility Principle: Why Each Class Should Do Only One Thing

The Single Responsibility Principle (SRP), part of the SOLID design guidelines, states that a class should have only one reason to change. Developers often bundle multiple functions — such as validation, password hashing, database storage, and email sending — into a single class for convenience, which makes the code fragile and hard to maintain. When a change in one area, like updating an email template, risks breaking unrelated logic such as data validation, debugging becomes time-consuming and error-prone. SRP addresses this by splitting responsibilities into dedicated classes, each handling a single concern, which improves testability, clarity, and flexibility. The practical result is that swapping out one component, such as an email provider, no longer risks introducing bugs in unrelated parts of the codebase.