Assign multiple variables at once in scala

Question

I have the following code:

val text = "some text goes here"
val (first, rest) = text.splitAt(4)
println(first + " *" + rest)

That works fine.

However, I want to have two cases, defining "first" and "rest" outside, like this:

val text = "some text goes here"
var (first, rest) = ("", "")
if (text.contains("z")) {
  (first, rest) = text.splitAt(4)
} else {
  (first, rest) = text.splitAt(7)
}
println(first + " *" + rest)

But that gives me an error:

scala>      | <console>:2: error: ';' expected but '=' found.
         (first, rest) = text.splitAt(4)

Why is it an error to do (first, rest) = text.splitAt(4) but not to do val (first, rest) = text.splitAt(4)? And what can I do?

Edit: Can't re-assign val, changed to var. Same error

Answer 1

The answer by Serj gives a better way of writing this, but for an answer to your question about why your second version doesn't work, you can go to the Scala specification, which makes a distinction between variable definitions and assignments.

From "4.2 Variable Declarations and Definitions":

Variable definitions can alternatively have a pattern (§8.1) as left-hand side. A variable definition var p = e where p is a pattern other than a simple name or a name followed by a colon and a type is expanded in the same way (§4.1) as a value definition val p = e, except that the free names in p are introduced as mutable variables, not values.

From "6.15 Assignments":

The interpretation of an assignment to a simple variable x = e depends on the definition of x. If x denotes a mutable variable, then the assignment changes the current value of x to be the result of evaluating the expression e.

(first, rest) here is a pattern, not a simple variable, so it works in the variable definition but not in the assignment.

Answer 2

First of all val is immutable, so you can't reassign it. Second, if, like all control structures in Scala, can return a value. So, you can do it like this:

val text = "some text goes here"
val (first, rest) = if (text.contains("z")) text.splitAt(4) else text.splitAt(7)
println(first + " *" + rest)