object FooSeq { def unapplySeq(x:Any): Option[Product2[Int,Seq[String]]] = { if (x.isInstanceOf[Bar]) { val y = x.asInstanceOf[Bar] Some(y.size, y.name) } else None } def main(args:Array[String]) = { val b = new Bar b match { case FooSeq(s:Int,_,n:String) => Console.println("size " + s +" name "+ n) } b.size = 54 b.name = List("large","L") b match { case FooSeq(s:Int,_,n:String) => Console.println("size " + s +" name "+ n) } } } class Bar { var size: Int = 50 var name: Seq[String] = List("medium","M") }