Explore creating robust HTTP services in Scala's functional programming paradigm. Gain insights into pure vs. impure implementations, their pros and cons, and effective tool usage.

scala-platform.tar.gz

Scala-Pure

Scala-Impure

Scala-Tapir

Scala-Impure-Test

Scala-Pure-Test

Scala-Tapir-Test

Test

Scala - Run Code Widget 

Scala-Pure-copy

Scala is one of the most popular general-purpose languages that supports both object-oriented and functional programming. In this course, you will learn how to create back-end HTTP services using Scala's functional programming paradigm.

You will also learn how to develop, test, and document the service using both pure and impure ways. You will be exposed to the differences between pure and impure implementation, their respective pros and cons, and how pure implementation can be more robust in terms of performance, understandability, testability, and type safeness. 

By the end of the course, you will have a clear idea of how functional programming works in Scala and how you can use the available tools more effectively.

Pure Functional HTTP APIs in Scala

# Base for http4s routes

The routing DSL of http4s differs from the routing of Akka-HTTP. The latter makes it easier to model out a base for our routes. 




val productRoutes: HttpRoutes[IO] = HttpRoutes.of[IO] {
  case GET -> Root / "product" / id => 
    ???
  case PUT -> Root / "product" / id => 
    ???
}
val productsRoutes: HttpRoutes[IO] = HttpRoutes.of[IO] {
  case GET -> Root / "products" =>
    ??? 
  case POST -> Root / "products" => 
    ??? 
}


As we can see, the DSL is closer to Scala syntax and quite easy to read. But before we move on to the details of each route, let’s think about how this can be modelled to become a bit more abstract. 



# Routing classes

While it is fine to have our routes bound to `IO`, it would be better to have more flexibility. We have several options, but for starters, we just extract our routes into their own classes, like in the following schema: 

Learn how to set up a base for http4s and product routes.

Introduction

Impure Implementation

Pure Implementation

Testing Impure Services

Testing Pure Services

Benchmarks

Documentation

Epilogue

Http4s Routes

Base for http4s routes

Routing classes