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

## Repository base

As we have already started using a tagless final approach, we will continue with it and define a base for our repository. 



trait Repository[F[_]] {
  def loadProduct(id: ProductId): F[Seq[(ProductId, LanguageCode, ProductName)]]
  
  def loadProducts(): Stream[F, (ProductId, LanguageCode, ProductName)]
  
  def saveProduct(p: Product): F[Int]
  
  def updateProduct(p: Product): F[Int]
}

We are feeling braver now and are attempting to use proper refined types in our database functions. This is possible due to the usage of the *doobie-refined* module.

To be able to map the `UUID` data type (and others), we also need to include the *doobie-postgresql* module. For convenience, we are still using `ProductId` instead of `UUID` in our definition. In addition, we wire the return type of `loadProducts` to be a `fs2.Stream` because we want to achieve pure functional streaming here.

Let’s see what a repository using *Doobie* looks like. 

# Repository base

As we have already started using a tagless final approach, we will continue with it and define a base for our repository. 



Learn how to integrate the database with Doobie.

Introduction

Impure Implementation

Pure Implementation

Testing Impure Services

Testing Pure Services

Benchmarks

Documentation

Epilogue

Doobie

Repository base