ZIO learning - structured services - the basic pattern / published by https://github.com/dacr/code-examples-manager #4ea028bc-f9f8-4c18-a0f9-42684a733dde/8ab0d89f67354ecbb3d6529483a651e9222e4de9

zio-learning-26-structured-services-1.sc

// summary : ZIO learning - structured services - the basic pattern
// keywords : scala, zio, learning, services, pure-functional, @testable
// publish : gist
// authors : Rock the JVM
// license : Apache NON-AI License Version 2.0 (https://raw.githubusercontent.com/non-ai-licenses/non-ai-licenses/main/NON-AI-APACHE2)
// id : 4ea028bc-f9f8-4c18-a0f9-42684a733dde
// created-on : 2021-05-03T18:04:46+02:00
// managed-by : https://github.com/dacr/code-examples-manager
// run-with : scala-cli $file

// Highly inspired from Structuring Services in Scala with ZIO and ZLayer : https://www.youtube.com/watch?v=PaogLRrYo64
// And lately updated or Scala3 & ZIO2

// ---------------------
//> using scala "3.4.2"
//> using dep "dev.zio::zio:2.0.13"
// ---------------------
import zio.*

// ----------------------------------------------------------------------------------------
case class User(name: String, email: String)

// ----------------------------------------------------------------------------------------
// This is the classical service pattern used within ZIO, with the standard naming scheme

// Service definition
trait UserEmailer:
  def notify(user: User, message: String): Task[Unit]

object UserEmailer:

  class UserEmailerImpl() extends UserEmailer:
    override def notify(user: User, message: String): Task[Unit] =
      ZIO.attempt(println(s"[User emailer] Sending '$message' to ${user.email}'"))

  val live: URLayer[Any, UserEmailer] = ZLayer.succeed(UserEmailerImpl())

  // Front-facing API - helper function
  def notify(user: User, message: String): RIO[UserEmailer, Unit] =
    ZIO.serviceWithZIO(_.notify(user, message))

// ----------------------------------------------------------------------------------------

object Encapsulated extends ZIOAppDefault:
  val david   = User("david", "[email protected]")
  val message = "Welcome to this site !"

  val logic =
    UserEmailer
      .notify(david, message)         // the kind of effect
      .provideLayer(UserEmailer.live) // provide the input for that effect

  override def run = logic.exitCode

Encapsulated.main(Array.empty)