SOLID as a Rock

Interface Segregation

The Interface Segregation Principle (ISP) emphasizes creating smaller, more specific interfaces to enhance code maintainability and flexibility. Joe Zack highlights that a method should only interact with the parts of an interface it needs, using a car braking system as an example where only relevant information is required 1. This approach prevents the need to implement unnecessary methods, as Alan Underwood points out with the .NET membership provider example, which requires implementing numerous methods for simple tasks 1.

If your interface requires a lot of methods to be implemented that often aren't needed, your code smells.

--- Michael Outlaw

Alan also notes that smaller interfaces simplify unit testing, as they allow for easier creation of mock classes 2.

   

Interface Implementation

Implementing interfaces effectively involves organizing them in a way that maintains clarity and flexibility. Joe Zack and Alan Underwood discuss the importance of keeping interfaces concise and organized, suggesting methods like placing them in separate folders or even within the same file for small classes 2. This organization aids in maintaining a clean codebase, especially when adhering to SOLID principles, which often result in numerous small classes.

If you're following these solid principles, you're probably going to end up with so many freaking classes that you can't really use the file explorer much anyway.

--- Joe Zack

Michael Outlaw adds that understanding the substitutable nature of interfaces can prevent code smells, such as unnecessary type checks, which complicate code maintenance 3.