How to do this with Scala generic

Question

Currently I have couple of methods that are very similar and I would like to merge them into 1 method. Here are the 2 methods

  def toInt(attrType: String, attrValue: String): Int = {
    attrType match {
      case "N" => attrValue.toInt
      case _ => -1
    }
  }

  def toString(attrType: String, attrValue: String): String = {
    attrType match {
      case "S" => attrValue
      case _ => ""
    }
  }

I am thinking there is an easier way to do this in Scala using generic?

The question is: What do you want to simplify? In this example, the only thing which has code duplicates is the `attrType match {`. The rest is to different to make it more generic. — kiritsuku, Aug 04 '12 at 10:01
The actual code is more complicated than what I showed, I simplified it for the question. — Bob, Aug 05 '12 at 05:35

score 3 · Accepted Answer · answered Aug 04 '12 at 07:24

You could do the following:

trait Converter[T] {
  def convert(attrType: String, attrValue: String): T
}

object ConverterTest {

  implicit object IntConverter extends Converter[Int] {
    def convert(attrType: String, attrValue: String): Int = {
      attrType match {
        case "N" => attrValue.toInt
        case _ => -1
      }
    }
  }

  implicit object StringConverter extends Converter[String] {
    def convert(attrType: String, attrValue: String): String = {
      attrType match {
        case "S" => attrValue
        case _ => ""
      }
    }
  }

  def to[T: Converter](attrType: String, attrValue: String): T = {
    implicitly[Converter[T]].convert(attrType, attrValue)
  }

  def main(args: Array[String]) {
    println(to[String]("S", "B"))
    println(to[String]("N", "B"))

    println(to[Int]("S", "23"))
    println(to[Int]("N", "23"))
  }
}

Its more code, and I couldn't get type inferencing to work, so it is probably of limited use.

But it is a single method plus a bunch of converters that can get controlled at the call site, so you get some extra flexibility.

Is it worth the effort? Depends on the actual use case.

Gallant effort but as you said, is it worth the effort, probably not. Thanks. — Bob, Aug 05 '12 at 05:34

How to do this with Scala generic

1 Answers1