Killing Speculative Generality Code Smell
I’m just reviewing a project’s code. I found a common pattern used in their code base. Every class implements an Interface. Each interface is only implemented by one class. Even more interesting, this interface is not exposed outside. In other words, its not exposed as part of the API.
Then my question is
Why do we need the interface? Why can’t we just use the class directly?
Apparently there is no valid answer. Some told me,
- Spring forces you to have interfaces.
- That’s not true.
- Some told me their mocking framework does not support mocking a class.
- This is also not true. Most mocking frameworks come with a class extension. Some new frameworks, don’t even distinguish between an interface and a class.
Anyway, we don’t need one stupid interface for every class we create. YAGNI. When we need it, we’ll create it. This is one form of speculative generality code smell.
Go ahead, kill it!
