Check if a string is blank or doesn't exist in Scala

Question

I have an Option[String].

I want to check if there is a string exists and if it\'s exists its not blank.

def isBlank( input : Option[Strin         


        

Answer 1

I added a Scalafiddle to play with that: Scalafiddle

That shows the marked correct answer is wrong (as pointed out by prayagupd):

def isBlank(str: Option[String]): Boolean =
   str.forall(_.trim.isEmpty)

the solution is for non-blank:

def isNotBlank(str: Option[String]): Boolean =
   str.exists(_.trim.nonEmpty)   

Answer 2

You can also take advantage of Extractor pattern. It makes codes much more declarative.

For example:

object NonBlank {
  def unapply(s: String): Option[String] = Option(s).filter(_.trim.nonEmpty) 
}

And then use it like

def createUser(name: String): Either[Error, User] = name match {
  case NonBlank(username) => Right(userService.create(username))
  case _ => Left(new Error("Invalid username. Blank usernames are not allowed."))
}

Answer 3

you can also check using lastOption or headOption

if the string is empty it will return None

scala> "hello".lastOption
res39: Option[Char] = Some(o)

scala> "".lastOption
res40: Option[Char] = None