Exception handling to Either

ExceptionHandlingExamplesTest.scala

import org.scalatest.{Matchers, WordSpecLike}

import scala.util.{Failure, Success, Try}

object ExceptionHandlingExamples {

  case class CaseClass(a: Int, b: Int)

  def parseUsingMatchOnTry(str: String): Either[String, CaseClass] =
    str.split("_") match {
      case Array(a, b) =>
        Try(CaseClass(a.toInt, b.toInt)) match {
          case Success(c) => Right(c)
          case Failure(e) => Left(s"Error parsing ${str} => ${e.getMessage}")
        }
      case _ => Left(s"[${str}] is not a valid format for a CaseClass")
    }

  def parseUsingEitherIsomorphism(str: String): Either[String, CaseClass] =
    str.split("_") match {
      case Array(a, b) =>
        Try(CaseClass(a.toInt, b.toInt)).toEither.left
          .map(e => s"Error parsing ${str} => ${e.getMessage}")
      case _ => Left(s"[${str}] is not a valid format for a CaseClass")
    }

  def parseUsingFold(str: String): Either[String, CaseClass] =
    str.split("_") match {
      case Array(a, b) =>
        Try(CaseClass(a.toInt, b.toInt))
          .fold(
            e => Left(s"Error parsing ${str} => ${e.getMessage}"),
            tileIdx => Right(tileIdx)
          )
      case _ => Left(s"[${str}] is not a valid format for a CaseClass")
    }

}

class ExceptionHandlingExamplesTest extends WordSpecLike with Matchers {

  import ExceptionHandlingExamples._

  "ExceptionHandlingExamples" when {

    "uses match on Try" in {
      parseUsingMatchOnTry("1_2") shouldBe Right(CaseClass(1, 2))
      parseUsingMatchOnTry("X_Y") shouldBe Left(
        "Error parsing X_Y => For input string: \"X\""
      )
    }

    "uses either isomorphism" in {
      parseUsingEitherIsomorphism("1_2") shouldBe Right(CaseClass(1, 2))
      parseUsingEitherIsomorphism("X_Y") shouldBe Left(
        "Error parsing X_Y => For input string: \"X\""
      )
    }

    "uses fold" in {
      parseUsingFold("1_2") shouldBe Right(CaseClass(1, 2))
      parseUsingFold("X_Y") shouldBe Left(
        "Error parsing X_Y => For input string: \"X\""
      )
    }

  }
}