daimonscala#21

RemoteCalculator.scala

import scala.util.control.Exception._

class ServerIsDownException extends Exception

object A extends App {

  val remoteCalculatorService = new AnyRef {
    def add(a: Int, b: Int): Int = {
      a + b match {
        case odd if odd % 2 == 1 => odd
        case _ => throw new ServerIsDownException
      }
    }
    def close() = {}
  }

  val log = new AnyRef {
    def error[A <: Throwable](t: A, m: String): Unit = println(m)
  }

  def using[A, R <: { def close() }](r : R)(f : R => A) : A =
    try { f(r) } finally { r.close() }

  def remote_add(a: Int, b: Int): Either[Throwable, Int] =
    using (remoteCalculatorService) { service =>
      catching(classOf[ServerIsDownException]).either {
        service.add(a, b)
      }
    }

  def add(a: Int, b: Int): Int =
    remote_add(a, b) match {
      case Right(x) => x
      case Left(t) => log.error(t, "the remote ...."); 0
    }

  println("1 + 2 =" + add(1, 2))
  println("1 + 1 =" + add(1, 1))
}

new AnyRef{

って単に

new {

って書けるよ！
(たぶん意味同じだったはず)

fmfm