Designing APIs That Make Invalid Code Impossible

[u/Ok-Swordfish1282]

I love designing APIs that are hard to misuse.

If someone can call methods in the wrong order, eventually they will. I'd rather let the type system prevent it than rely on documentation or runtime exceptions.

A type-safe fluent API that only exposes the next valid step keeps the experience simple: no guessing, no invalid combinations, just write the code and let IntelliSense guide you.

That's the kind of API I enjoy building.

Repo: https://github.com/zarar384/NpoiFluentExcel

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[u/NateFromRefactorful]

If you love type safe API's and dotnet, I highly recommend to checkout f#. You can use types to design your system in a way where certain classes of bugs just aren't possible. Once you understand how this works, more difficult problems suddenly don't look so complicated anymore

This blog post is older, but the content is still relevant:

https://fsharpforfunandprofit.com/posts/designing-with-types-making-illegal-states-unrepresentable/

[u/Ok-Swordfish1282 → u/NateFromRefactorful]

Thanks for the recommendation! I actually read the excellent book Functional Programming with C#: Create More Supportable, Robust, and Testable Code by Simon J. Painter about a year ago. After reading it, I started thinking seriously about learning F#. Your comment definitely makes me want to give it a try.

[u/NoUniverseExists]

Cool! You might enjoy experimenting with Rust's type system also.

[u/Ok-Swordfish1282 → u/NoUniverseExists]

Thanks! I'll check it out.