scala の validation イディオム - Qiita

case class Person(val name:String) object Hello { def validate(p:Person):Either[String,Boolean] = for { _ <- checkNotNull(p).right v <- checkNotNullAndEmpty(p.name).right } yield v def checkNotNull[A](a:A):Either[String,Boolean] = if (a==null) Left("is null") else Right(true) def checkNotNullAndEmpty[A](s:String):Either[String,Boolean] = { if (s==null) Left("is null") else if (s=="") Left("is empt