Scala Listing and Reading

Question

Scala Enumerationand the method Enumeration.Val readResolvedo not work as they should (possibly related to this entry in Scala trac ). Here is the program provided by * Steve Bendiola to illustrate the problem:

@serializable
object InvestmentType extends Enumeration {
  val Debt = Value("DEBT")
  val Future = Value("FUTURE")
  val Equity = Value("EQUITY")
}

Now there is a class Mainthat can be launched either using arument W, where it will write the enumeration values ​​to a file, or Rwhere it will read them again:

object Main {
  def main(args: Array[String]) = {
    args(0) match {
      case "R" => {
        val ois = new ObjectInputStream(new FileInputStream("enum.ser"))
        var obj: Object = null

        foreach(ois) { obj =>
              obj match {
                case InvestmentType.Debt => println("got " + obj)
                case InvestmentType.Equity => println("got " + obj)
                case InvestmentType.Future => println("got " + obj)
                case _ => println("unknown: " + obj + " of: " + obj.getClass)
              }
        }
      }

      case "W" => {
        val oos = new ObjectOutputStream(new FileOutputStream("enum.ser"))
        InvestmentType.foreach {i => oos.writeObject(i)}
        oos.flush
        oos.close
      }
    }
  }

Both of these methods require this method foreach:

  def foreach(os: ObjectInputStream)(f: Object => Unit) {
    try {
      val obj = os.readObject
      if (obj != null) {
        f(obj)
        foreach(os)(f)
      }
    } catch {
      case e: EOFException => //IGNORE
    }
  }
}

The output of this program should not look like this:

got DEBT
unknown: FUTURE of: class scala.Enumeration$Val
unknown: EQUITY of: class scala.Enumeration$Val

This seems to be due to the order announced. Reordering them, it seems that the first value is always reasonably resolved

Answer 1

Scala hashCode Value Enumeration , . . :

object InvestmentType extends Enumeration {
  val Debt = Value(1, "DEBT")
  val Equity = Value(2, "EQUITY")
  val Future = Value(3, "FUTURE")
}

, , .

.