gvolpe

Dependency Injection in Functional Programming

There exist several DI frameworks / libraries in the Scala ecosystem. But the more functional code you write the more you'll realize there's no need to use any of them.

A few of the most claimed benefits are the following:

• Dependency Injection.
• Life cycle management.
• Dependency graph rewriting.

gvolpe

//> using scala "3.3.0-RC1"
//> using lib "org.typelevel::cats-effect:3.4.5"
//> using plugin "com.github.ghik:::zerowaste:0.2.3"
//> using options "-Wunused:imports"
//> using options "-Werror"
//> using options "-Wvalue-discard"

import cats.effect.*

object Main extends IOApp.Simple:

gvolpe

import cats.Traverse
import cats.effect._
import cats.effect.concurrent.Semaphore
import cats.temp.par._
import cats.syntax.all._

import scala.concurrent.duration._

object Main extends IOApp {
  import ParTask._

gvolpe

ThisBuild / scalaVersion := "2.13.5"

lazy val root = (project in file("."))
  .settings(
    name := "minimal",
    libraryDependencies ++= Seq(
      compilerPlugin(
        "org.typelevel" %% "kind-projector" % "0.11.3"
          cross CrossVersion.full
      ),

gvolpe

import java.util.concurrent.Future

import cats.effect.{Effect, Sync, Timer}
import cats.syntax.all._
import fs2._
import fs2.async.mutable.Signal

import scala.concurrent.ExecutionContext
import scala.concurrent.duration._

gvolpe

import cats.effect._
import cats.syntax.functor._
import fs2._
import java.nio.file.Paths
import java.util.concurrent.Executors
import scala.concurrent.ExecutionContext
import scala.util.Try

object CsvApp extends IOApp {

gvolpe

Scalafmt config

How can I get scalafmt to format my case class like this?

case class Person(
    name: String,
    age: Int
) derives Eq, Show

gvolpe

import cats.{ ApplicativeError, MonadError }
import cats.data.{ Kleisli, OptionT }
import cats.effect.Sync
import cats.effect.concurrent.Ref
import cats.syntax.all._
import io.circe.generic.auto._
import io.circe.syntax._
import org.http4s._
import org.http4s.circe.CirceEntityDecoder._
import org.http4s.circe._

gvolpe

import eu.timepit.refined._
import eu.timepit.refined.api.Refined
import eu.timepit.refined.auto._
import eu.timepit.refined.string.MatchesRegex

object refinements {
  type EmailPred = MatchesRegex[W.`"""(?=[^\\s]+)(?=(\\w+)@([\\w\\.]+))"""`.T]
  type Email = String Refined EmailPred
}

gvolpe

import java.util.UUID

import monocle.Iso

trait IsUUID[A]:
  def iso: Iso[UUID, A]

object IsUUID:
  def apply[A](using ev: IsUUID[A]): IsUUID[A] = ev