Scala example source code file (Resource.scala)

This example Scala source code file (Resource.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.

Learn more about this Scala project at its project page.

Java - Scala tags/keywords

closeable, contravariant, resource

The Resource.scala Scala example source code

package scalaz
package effect

////
import java.io.Closeable

/**
 *
 */
////
trait Resource[F]  { self =>
  ////

  def close(f: F): IO[Unit]

  // derived functions
  def contramap[G](f: G => F): Resource[G] = new Resource[G] {
    def close(g: G): IO[Unit] = self.close(f(g))
  }

  ////
  val resourceSyntax = new scalaz.syntax.effect.ResourceSyntax[F] { def F = Resource.this }
}

object Resource {
  @inline def apply[F](implicit F: Resource[F]): Resource[F] = F

  ////

  def resource[A](closeAction: A => IO[Unit]): Resource[A] =
    new Resource[A] {
      def close(a: A): IO[Unit] = closeAction(a)
    }

  def resourceFromCloseable[A <: Closeable]: Resource[A] =
    resource(a => IO(a.close))

  implicit val contravariant: Contravariant[Resource] =
    new Contravariant[Resource] {
      def contramap[A, B](fa: Resource[A])(f: B => A): Resource[B] =
        fa.contramap(f)
    }

  ////
}