When using the `when` expression to test some case...

# announcements

[voben]

When using the when expression to test some cases, why do I have to use the is keyword sometimes, and other times I don’t?

[Mike]

is compares Types. It's an operator of sorts.

[voben]

But sometimes its the IDE forces me to add the is keyword and other times it doesn’t, why is that the case?

[Dominaezzz]

I'm guessing is won't be required is it's an object ?

[voben]

that’s correct, but is there a reason for this?

[Vlad]

is is basically an instanceOf check. Enums and objects are singletons so there is no need to perform an instanceOf comparison

[voben]

great, thank you

[Dominaezzz]

The questions has been answered but I don't want to discard mine, so I'll leave it here. 😅


Say we have.

sealed class Example
data class Wrap(val value: Int): Example()
object None : Example()

val tmp: Example = TODO(...)

I think it's because you can do if (tmp == None) or if (tmp is None) but you can only do if (tmp is Wrap) . I'm sure you know why if (tmp == Wrap) doesn't work.

[arekolek]

I use is when checking for `object`s anyway. This way when looks less cluttered and if later I decide to convert the object to a data class I don’t have to change the code in every when it occurred

[arekolek]

And I’m not the only one to prefer it this way https://kotlinlang.slack.com/archives/C4GKV43N2/p1562270360031400