Kotlin: handling exception when defining a val

Question

I'm working on a kotlin web backend and have something like this:

try {
    val uuid = UUID.fromString(someString)
} catch (e: IllegalArgumentException) {
    throw BadRequestException("invalid UUID")
}

doSomething(uuid)

The code above doesn't compile since uuid is unresolved outside the try block.

Alternatives I can imagine are:

move doSomething(uuid) inside the try block, but I'd rather avoid that so I don't accidentally catch some other potential IllegalArgumentException thrown by doSomething (if that happens for whatever reason I want things to fail and get a 500 in my logs so I can investigate)
use a nullable var instead and initialize it to null but that seems a bit ugly?

This throw BadRequestException pattern is working well otherwise so I don't want to change the return type of the method or something like that in order to avoid throwing.

Is there a better / more elegant / recommended pattern for this in Kotlin?

Tenfour04 · Accepted Answer · 2020-12-23 23:03:44Z

5

In Kotlin, try/catch can be used as an expression. Branches that throw don't affect the resolved type. So you can write:

val uuid = try {
    UUID.fromString(someString)
} catch (e: IllegalArgumentException) {
    throw BadRequestException("invalid UUID")
}

answered Dec 23, 2020 at 23:03

Tenfour04

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