CODEWITHSUNDEEP
scalacoding-stylepattern-matchingfor-comprehension
James Davies
James Davies

Reputation: 9859

Scala - Pattern matching result of a for comprehension

I'm currently performing a pattern match on the result of a for-comprehension as follows

val validXsrf = for(
    cookie <- request.cookies.get("XSRF-TOKEN"); 
    header <- request.headers.get("X-XSRF-TOKEN"); 
    if cookie.value == header ) yield true;

validXsrf match {
   case Some(true) => callbackFunc();
   case None       => throw new XsrfException();
}

However this feels a little overly verbose - is there a cleaner way of expression this?

Ideally I'd love to do something like

for(....) match { .... }

However this does not appear possible in Scala without wrapping the entire for-comprehension in brackets.

Is there a cleaner / more elegant way of expressing this logic?

Upvotes: 0

Views: 821

Answers (1)

cmbaxter
cmbaxter

Reputation: 35453

You could abbreviate things a bit like this (assuming callbackFunc returns a String):

def validXsrf():String = {
  val xsrf = for{
    cookie <- request.cookies.get("XSRF-TOKEN")
    header <- request.headers.get("X-XSRF-TOKEN") 
    if cookie.value == header
  } yield callbackFunc()

  xsrf.getOrElse(throw new XsrfException())
}

Now if you didn't want to throw the exception on the failure case, you could redefine the validXsrf method around returning a Try instead, something like this:

def validXsrf():Try[String] = {
  val xsrf = for{
    cookie <- request.cookies.get("XSRF-TOKEN")
    header <- request.headers.get("X-XSRF-TOKEN") 
    if cookie.value == header
  } yield callbackFunc()

  xsrf.fold[Try[String]](Failure(new XsrfException()))(Success(_))
}

Upvotes: 2

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