Purely Functional HTTP clients for Free

Interfacing with external APIs is now part of almost every backend service. In essence, making HTTP calls involves side effects, and, as everyone who’s had to test side effects knows, they are often a pain to test. Can we do something to integrate with these external services in a pure and functional way, and make them simpler to test? I say we can, with the Free monad.

I’ll introduce an imperative HTTP client and gradually transform it into a purely functional one. Then I’ll show how it can be used in Web API clients and how it all makes testing trivial.

Session length

40 minutes

Language of the presentation

English

Target audience

Intermediate: Requires a basic knowledge of the area

Who is your session intended to

people who want to write side-effect-free applications using HTTP APIs

Speaker

Jakub Kozłowski (Scala developer, Scalac)