I need to check if an object is any of 4 possible ...

# getting-started

[Marcin Wisniowski]

I need to check if an object is any of 4 possible types, is there any cleaner way than item is A || item is B || item is C || item is D?

[Joffrey]

I think it depends on how you want to use this condition.

If your goal here is to avoid repeating the item subject, you could use a when like this:

when (item) {
    is A, is B, is C, is D -> doTheThing()
    else -> dontDoTheThing()
}

[Joffrey]

The best would of course be to define a parent type for A, B, C, and D and check if item is of the parent type (e.g. a sealed interface)

[Marcin Wisniowski]

It is a sealed interface with 8 types, but I need to check if it's any of 4 of them. It's inside a list filter {}

[Marcin Wisniowski]

I guess I could define a separate empty interface to "mark" these 4.

[Joffrey]

Exactly

[Joffrey]

and if there is something so special about these 4 types that they are treated in a common way, maybe they share properties, or should have common methods, which would go into that interface

[Joffrey]

Using a parent interface also allows to use .filterIsInstance<TheParentInterface>() which yields a list of the new element type, which allows to make use of this information further down the pipeline

[Marcin Wisniowski]

It's actually a list of object that have the interesting items as a field, so it's now `.filter { it.item is MarkerInterface }``

[Joffrey]

Got it, it will depend on the use case of course