SOLID series: Understanding the Interface Segregation Principle (ISP)

Interface Segregation Principle (ISP)

The Interface Segregation Principle (ISP) states that no code should be forced to depend on methods that it does not use. It ensures that classes implement interfaces tailored to their specific needs, keeping the code lean and maintainable.

Problem with Bloated Interfaces

Bloated interfaces, also known as "fat interfaces," contain too many irrelevant methods, making it difficult for developers to work with them. They lead to counterintuitive systems where the purpose of a class is obscured.

Interface Segregation Refactor

To address bloated interfaces, the Interface Segregation Refactor involves splitting a large interface into smaller, focused ones. This allows classes to implement interfaces that align with their specific functionalities, promoting clarity and maintainability.

Application of ISP in API Design

When an API is overloaded, it exposes unnecessary methods to clients, violating the principles of ISP. Designing interfaces based on class needs ensures that only relevant methods are exposed to the clients.

ISP vs. SRP

While the ISP focuses on segregating interfaces based on class needs, the Single Responsibility Principle (SRP) emphasizes that a class should have only one reason to change. Both principles work together to create well-structured and maintainable code.