Scala で Active Patterns っぽいことやってみた

fizzbuzz.scala

class FizzBuzzExtractor[T](f: T => Boolean){
  def unapply(t: T) = f(t)
}

val FizzBuzz = new FizzBuzzExtractor[Int](_ % 15 == 0)
object Fizz extends FizzBuzzExtractor[Int](_ % 3 == 0)
object Buzz extends FizzBuzzExtractor[Int](_ % 5 == 0)

object FizzBuzzRunner {
  def run(num: Int) = num match {
    case FizzBuzz() => println("FizzBuzz")
    case Fizz() => println("Fizz")
    case Buzz() => println("Buzz")
    case num => println(num.toString())
  }
}

FizzBuzzRunner.run(1)   //=> 1
FizzBuzzRunner.run(3)   //=> Fizz
FizzBuzzRunner.run(4)   //=> 4
FizzBuzzRunner.run(5)   //=> Buzz
FizzBuzzRunner.run(10)  //=> Buzz
FizzBuzzRunner.run(15)  //=> FizzBuzz