Structural subtyping in Scala

You can specify a type bound that require a type to support certain methods:

object Example2 {
  def using[T <: {def close(): Unit}, S](obj: T)
                                        (operation: T => S) = {
    val result = operation(obj)
    obj.close()
    result
  }
  val str = using(new BufferedReader(new InputStreamReader(new FileInputStream("/tmp/readme")))) {
    obj => {
      val res = obj.readLine()
      res match {
        case null => None
        case x => Some(x)
      }
    }
  }
}