[constraint] Checking if both fields are assigned

[greenoctopus20]

I'm struggling to check if 2 variables are assigned.
I have this class and I want to make sure that when it's amends/eval only 1 variable from [regex,regex2] is assigned

open class Component {
    ....
    regex: String?
    regex2: String?
    ....
}

I want to do something like this

 if regex is not null and regex2 is not null then throw("only one from regex and regex2, should be assigned not both")

or something like

exception = if (!isNaN regex && !isNaN regex2) throw("one needs to be assigned") else "Good"

How I can approach this with if-else or maybe constraint to throw an exception if both values are assigned
Thank you

[greenoctopus20]

Solved

exception = if (regex != null && regex2 != null) throw("one of regex/regex2 needs to be assigned") else "Good"