This is a noob question and may have been asked before, but what does the when block do by default i...

# getting-started

[Steven McLaughlin]

This is a noob question and may have been asked before, but what does the when block do by default if a case is not found? Like in the following example, what is actually happening when I pass BAD into that function? Essentially, I want to make the when block exhaustive but not change the behavior of the function.

enum class SomeEnum {
    GOOD,
    BAD
}

fun doTheEnumThing(someEnum: SomeEnum) {
            when (someEnum) {
                SomeEnum.GOOD -> println("good")
            }
}

[Ruckus]

To answer your question, nothing. It works the same as

fun doTheEnumThing(someEnum: SomeEnum) {
    if (someEnum == SomeEnum.GOOD) {
        println("good")
    }
}

There's no else statement, so nothing happens. It just returns.

[Steven McLaughlin]

What I'm trying to figure out is like.. what would I put in the BAD case so that it has the same behavior? Just something like this?

when (someEnum) {
                SomeEnum.GOOD -> println("good")
                SomeEnum.BAD -> return
            }

[Ruckus]

If there isn't a bad case, why do you want to add a stub for one? But if you do want it, you could do

SomeEnum.BAD -> Unit
// or
SomeEnum.BAD -> {}

[pavel]

that would return out of the function which might not be what you want

[Ruckus]

@pavel I assume that was meant for @Steven McLaughlin's code block and not mine, correct?

[pavel]

yes

[Steven McLaughlin]

Cool. I mostly want to stub one because the ide is giving me warnings haha

[Ruckus]

You should probably also add a comment to make it clear it wasn't a mistake

SomeEnum.BAD -> Unit  // Do Nothing
// or
SomeEnum.BAD -> {}  // Do Nothing

[cedric]

Note that if your when is a value for an expression, the compiler will mandate exhaustiveness