Scala example source code file (FromString.scala)

This example Scala source code file (FromString.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

argumentsfromstring, directory, existingdirrelativeto, fromstring, intfromstring, none, optmanifest, reflection, string, stringfromstring, t

The FromString.scala Scala example source code

/* NSC -- new Scala compiler
 * Copyright 2005-2013 LAMP/EPFL
 * @author  Paul Phillips
 */

package scala.tools
package cmd

import nsc.io.{ Path, File, Directory }
import scala.reflect.OptManifest

/** A general mechanism for defining how a command line argument
 *  (always a String) is transformed into an arbitrary type.  A few
 *  example instances are in the companion object, but in general
 *  either IntFromString will suffice or you'll want custom transformers.
 */
abstract class FromString[+T](implicit m: OptManifest[T]) extends PartialFunction[String, T] {
  def apply(s: String): T
  def isDefinedAt(s: String): Boolean = true
  def zero: T = apply("")

  def targetString: String = m.toString
}

object FromString {
  // We need this because we clash with the String => Path implicits.
  private def toDir(s: String)  = new Directory(new java.io.File(s))

  /** Path related stringifiers.
   */
  val ExistingDir: FromString[Directory] = new FromString[Directory] {
    override def isDefinedAt(s: String) = toDir(s).isDirectory
    def apply(s: String): Directory =
      if (isDefinedAt(s)) toDir(s)
      else cmd.runAndExit(println("'%s' is not an existing directory." format s))
  }
  def ExistingDirRelativeTo(root: Directory) = new FromString[Directory] {
    private def resolve(s: String) = (toDir(s) toAbsoluteWithRoot root).toDirectory
    override def isDefinedAt(s: String) = resolve(s).isDirectory
    def apply(s: String): Directory =
      if (isDefinedAt(s)) resolve(s)
      else cmd.runAndExit(println("'%s' is not an existing directory." format resolve(s)))
  }

  /** Argument expander, i.e. turns single argument "foo bar baz" into argument
   *  list "foo", "bar", "baz".
   */
  val ArgumentsFromString: FromString[List[String]] = new FromString[List[String]] {
    def apply(s: String) = toArgs(s)
  }

  /** Identity.
   */
  implicit val StringFromString: FromString[String] = new FromString[String] {
    def apply(s: String): String = s
  }

  /** Implicit as the most likely to be useful as-is.
   */
  implicit val IntFromString: FromString[Int] = new FromString[Int] {
    override def isDefinedAt(s: String)   = safeToInt(s).isDefined
    def apply(s: String)                  = safeToInt(s).get
    def safeToInt(s: String): Option[Int] = try Some(java.lang.Integer.parseInt(s)) catch { case _: NumberFormatException => None }
  }
}