Scala example source code file (IORef.scala)

This example Scala source code file (IORef.scala) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Scala by Example" ^TM.

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Java - Scala tags/keywords

ioref, iorefs, stref

The IORef.scala Scala example source code

package scalaz
package effect

import ST._

/**
 * A mutable reference in the IO monad. Note that unsafePerformIO will allow leaking
 * such a reference out of the monad, but any operations on a leaked reference are still monadic.
 */
sealed abstract class IORef[A] {
  val value: STRef[IvoryTower, A]

  def read: IO[A] = STToIO(value.read)

  def write(a: => A): IO[Unit] = STToIO(value.write(a) map (_ => ()))

  def mod(f: A => A): IO[A] = STToIO(value.mod(f) flatMap (_.read))
}

object IORef extends IORefs

trait IORefs {
  private[effect] def ioRef[A](v: STRef[IvoryTower, A]): IORef[A] = new IORef[A] {
    val value = v
  }
}