// Vals en el constructor son propiedades:
  // p = Person("fede","silva", 10 )
  // p.first
  case class Person( val first:String, val last:String, val age:Int )

  // Como si fuera statics:
  // Person.key
  object Person extends Mapper[Person] {

    def key = first

    val first = "first" is { _.first } // "name" is accesor
    val last  = "last"  is { _.last  }
    val age   = "age"   is { _.age   }

  }