Scala equivalent for 'matches' regex method?

Question

Struggling with my first (ever) Scala regex here. I need to see if a given String matches the regex: " animal<[a-zA-Z0-9]+,[a-zA-Z0-9]+> ".

So, some examples:

animal<0,sega>          =>    valid
animal<fizz,buzz>       =>    valid
animAl<fizz,buzz>       =>    illegal; animAl contains upper-case (and this is case-sensitive)
animal<fizz,3d>         =>    valid
animal<,3d>             =>    illegal; there needs to be something [a-zA-Z0-9]+ between '<' and ','
animal<fizz,>           =>    illegal; there needs to be something [a-zA-Z0-9]+ between ',' and '>'
animal<fizz,%>          =>    illegal; '%' doesn't match [a-zA-Z0-9]+
etc.

My best attempt so far:

val animalRegex = "animal<[a-zA-Z0-9]+,[a-zA-Z0-9]+>".r
animalRegex.findFirstIn("animal<fizz,buzz")

Unfortunately that's where I'm hitting a brick wall. findFirstIn and all the other obvious methods available of animalRegex all return Option[String] types. I was hoping to find something that returns a boolean, so something like:

val animalRegex = "animal<[a-zA-Z0-9]+,[a-zA-Z0-9]+>".r
if(animalRegex.matches("animal<fizz,buzz>")) {
    val leftOperand : String = getLeftOperandSomehow(...)
    val rightOperand : String = getRightOperandSomehow(...)
}

So I need the equivalent of Java's matches method, and then need a way to access the "left operand" (that is, the value of the first [a-zA-Z0-9]+ group, which in the current case is " fizz "), and then ditto for the right/second operand (" buzz "). Any ideas where I'm going awry?

Answer 1

To be able to extract the matched parts from your string, you'll need to add capture groups to your regex expression, like so (note the parentheses):

val animalRegex = "animal<([a-zA-Z0-9]+),([a-zA-Z0-9]+)>".r

Then, you can use Scala's pattern matching to check for a match and extract the operands from the string:

val str = "animal<fizz,3d>"
val result = str match {
    case animalRegex(op1,op2) => s"$op1, $op2"
    case _                    => "Did not match"
}

In this example, result will contain "fizz, 3d"