gistfile1.scala

    abstract class Strategy[T, V]() {
      def doSomething(x: Int): V
      def unDoSomething(x: V): T
    }

    class StrategyOne() extends Strategy[Int, String] {
      def doSomething(x: Int): String = {"..."}
      def unDoSomething(x: String): Int = {1}
    }
    
    class StrategyTwo() extends Strategy[Double, List[Int]] {
      def doSomething(x: Int): List[Int] = {List(1,2,3)}
      def unDoSomething(x: List[Int]): Double= {4.3}
    }
    
    class Worker[T, V](strategy: Strategy[T, V]) {
      def run() {
        val res = strategy.doSomething(5) //res is a T
        val res2 = strategy.unDoSomething(res) //res2 is a V
        println(res2)
      }
    }
    
    val worker1 = new Worker(new StrategyOne())
    val worker2 = new Worker(new StrategyTwo())
    
    val strategies = Map("one" -> new StrategyOne(), "two" -> new StrategyTwo())
    val worker = new Worker(strategies("one"))
    
    worker.run