Handling stringly-typed configuration (e.g. config files, system properties). This is a Scala IDE worksheet - you'd package up the code differently in a real app.

Config.scala

import scala.language.implicitConversions

object configs {

  // Options (e.g. from a config file or system properties), as key-value strings
  val opts = Map("min" -> "100", "path" -> "/home/user2")

  // Automatically wrap the default values in a Some 
  // (or can omit this and specify None to indicate lack of a default value)
  implicit def wrap[A](a: A) = Some(a) 

  // Implicit conversion for each output type we want:
  implicit def toString(s: String) = s   
  implicit def toInt(s: String) = s.toInt  
  implicit def toBoolean(s: String) = s.toBoolean 

  // Generic function that uses one of the implicits. 
  // Every setting must be present, or have a default.
  def get[A](key: String, default: Option[A] = None)(implicit convert: String => A): A =
    getOption(key, default).getOrElse(throw new Exception(key))
                                                  //> get: [A](key: String, default: Option[A])(implicit convert: String => A)A
  // Allow missing (optional) config settings   
  def getOption[A](key: String, default: Option[A] = None)(implicit convert: String => A): Option[A] =
     opts.get(key).map(convert).orElse(default)

  // now extract the desired options, with or without default values. 
  // Need to declare the types so we know which implicit to use.
  val min: Int = get("min", 10)                   //> min  : Int = 100
  val max: Int = get("max", 10)                   //> max  : Int = 10
  //val max2: Int = get("max") // Exception - missing value and no default
  val path: String = get("path")                  //> path  : String = /home/user2
  // or can specify lack of default explicitly:
  val path2: String = get("path", None)           //> path2  : String = /home/user2
  //val bad: Boolean = get("bad", None) // Exception - missing value and no default
  
  // Optional config settings
  val path3: Option[String] = getOption("path")   //> path3  : Option[String] = Some(/home/user2)
  val nopath: Option[String] = getOption("nopath")//> nopath  : Option[String] = None
}