The transformers now return a Result, with more detail on failure than an Option holds. See blog.jessitron.com for the purpose of this post.

gistfile1.txt

// from https://github.com/jessitron/BlogCode/blob/master/optionToCustom.scala

object transformers {

  def openFile(n: String) : Result[java.io.File] = {
  val f = new java.io.File(n) // catch IOException
    if (f.exists)
      Success(f)
    else
      Failure("File does not exist: " + n)    
  }

  def readFirstLine (f : java.io.File) : Result[String] = {
    val source = io.Source.fromFile(f)
    try {
      if (!source.hasNext) 
        Failure("File is empty") 
      else 
        Success(source.getLines.next)
    } finally {
      source.close
    }
  }

  def parseLine(line : String) : Result[SecretMessage] = {
    val ExpectedFormat = "The secret message is '(.*)'".r
    line match {
      case ExpectedFormat(secretMessage) => Success(SecretMessage(secretMessage))
      case _ => Failure("Invalid format")
    }
  }
}