Scala DSL for loading properties in Play!

config.scala

// Loading properties with Java API's is annoying...
// val someInt = play.configuration("some.int", 10).toInt
// val someBool = "true" == play.configuration("some.boolean", "true").toLowerCase

// This makes it nicer. It's specifically for play but can be easily changed.

object config {

    def string(name: String): Proption[String] = {
        Proption(Option(play.configuration(name)), name)
    }

    def boolean(name: String): Proption[Boolean] = {
        string(name) map ("true" == _.toLowerCase)
    }

    def int(name: String): Proption[Int] = {
        string(name) map (Integer parseInt _)
    }

    class ConfigurationException(message: String, arg: String) extends RuntimeException(message format arg)
}

case class Proption[T](option: Option[T], propName: String) {
    def or(t: T): T = option getOrElse t

    def ! : T = option match {
        case Some(t) => t
        case None    => throw new config.ConfigurationException("mandatory prop [%s] not defined", propName)
    }

    def map[B](f: T => B): Proption[B] = Proption(option map f, propName)
}

// usage...

object main {
  import config
  import config._

  val stringWithDefault = config string "string.with.default" or "default"
  val mandatoryString = config string "mandatory.string" !
  val intWithDefault = config int "int.with.default" or 100
  val mandatoryBoolean = config boolean "mandatory.boolean" !
  // ...
}