如何在Scala中从中获取实际值：正确（Vector（“ abc”））

Question

I'm using Gatling to test a WebSocket based service and in order to parse a json response I get I use the following:

val initiator = JsonPath.query("$.header.initiator", json).right.map(_.toVector)

Printing initiator tells me that this is :

Right(Vector(guest3075085133639688955@example.com))

Now to the beginner Scala question:

How do I get the actual string value "guest3075085133639688955@example.com" ?

I've understood that the Right is just a container, that contains a Vector with one value (the value I want), but how do I get to it ?! :)

I've tried this, but that just prints the same thing (Right(Vect....):

initiator.foreach{println}

Cheers, Niklas

Answer 1

• You can use right to get the RightProjection of the Either and get to get the value inside the Right .
• You can use head to get the first (and in your case only) element from the Vector .

Which looks like :

val initiator: Either[String, Vector[String]] = 
  Right(Vector("guest3075085133639688955@example.com"))

initiator.right.get.head
// String = guest3075085133639688955@example.com

You could also do a pattern match :

val Right(Vector(email)) = initiator
// email: String = guest3075085133639688955@example.com

Note that both ways only work when initiatior is a Right and the Vector inside has at least one element. Your question is not exactly clear how you would like to handle Left and/or an empty Vector .

---

If you want to handle all the failing cases in another way, you could use :

initiator match {
  case Right(Vector(email)) => email // ok
  case _ => // default -> fail
}

Answer 2

initiator.right.get from Either is unsafe. Because it throws an java.util.NoSuchElementException if it is a left value.

By pattern matching:

initiator match {
  // when it is a right value, which is a vector with single element
  case Right(Vector(s)) => println(s)
  // when it is a right value, which is a vector with empty or two or more elements.
  case Right(v) => ???
  // when it is a left value
  case Left(l) => ???
}

Answer 3

In acomment you clarified this is for a test case scenario. If you're using ScalaTest matchers you could do:

initiator should matchPattern{case Right(Vector("expected value")) => }