ZIO live session - Writing a simple application - legacy versus effect-based / published by https://github.com/dacr/code-examples-manager #b354e541-49ea-4c6c-aa60-a6497b0ac72f/8665375cc4c964a2c5b387ecbf8dfffc12ea172e

live-04.sc

// summary : ZIO live session - Writing a simple application - legacy versus effect-based
// keywords : scala, zio, live, demo, pure-functional, @testable
// publish : gist
// authors : David Crosson
// license : Apache NON-AI License Version 2.0 (https://raw.githubusercontent.com/non-ai-licenses/non-ai-licenses/main/NON-AI-APACHE2)
// id : b354e541-49ea-4c6c-aa60-a6497b0ac72f
// created-on : 2021-09-26T16:27:18+02:00
// managed-by : https://github.com/dacr/code-examples-manager
// run-with : scala-cli $file

// ---------------------
//> using scala "3.4.2"
//> using dep "org.slf4j:slf4j-simple:2.0.7"
//> using dep "dev.zio::zio:2.0.13"
//> using dep "dev.zio::zio-nio:2.0.1"
//> using dep "fr.janalyse::zio-worksheet:2.0.13.0"
// ---------------------

// =========================================================================================
// classic legacy code

{
  import org.slf4j.LoggerFactory
  import scala.io.Source

  def app() =
    val logger      = LoggerFactory.getLogger("default")
    logger.info("Application starts")
    val fileContent = Source.fromFile("live-04.sc").getLines()
    val count       = fileContent.size
    logger.info("line count is {}", count)
    logger.info("Application ends")
    println(count)

  println(app())
}

// =========================================================================================
// effect based programming

{
  import zio.*, zio.worksheet.*
  import zio.nio.file.*

  val app = for {
    _     <- ZIO.log("Application starts")
    lines <- Files.readAllLines(Path("live-04.sc"))
    count  = lines.size
    _     <- ZIO.log(s"line count is $count")
    _     <- ZIO.log("Application ends")
    _     <- Console.printLine(count)
  } yield ()

  app.unsafeRun
}

// - both are readable in the same way !
// - but the second one is quite safer, the type signature tells us that it can fail