FactoryMethod pattern (Design Patterns in Scala)

FactoryMethod.scala

// http://blog.designrecipe.jp/2011/01/03/factory-method-strategy/

abstract class ListPrinter {
  def printList(list: List[String]) {
    val comparator = createComparator
    list.sortWith(comparator).foreach(println)
  }

  protected def createComparator: (String, String) => Boolean
}

class DictionaryOrderListPrinter extends ListPrinter {
  override protected def createComparator: (String, String) => Boolean =
    (s1, s2) => s1 < s2
}

class LengthOrderListPrinter extends ListPrinter {
  override protected def createComparator: (String, String) => Boolean =
    (s1, s2) => s1.size < s2.size
}

object FactoryMethodPatternExampleWiki {
  def main(args: Array[String]) = {
    val strs = List("apple", "plum", "pineapple")
    println("alphabetical sort:")
    (new DictionaryOrderListPrinter).printList(strs)
    println("length ordered sort:")
    (new LengthOrderListPrinter).printList(strs)
  }
}