Kotlin - Check if an object implements a specific interface

Question

Say I have some data class like:

data class NameCreated(
    val index: Float,
    val name: String
) : ESEventPayload

I then have some method where I want to return true if the Event's type in <Event<out Any>> is implementing ESEventPayload.

So for example:

fun isItUsing(message: AcknowledgeableMessage<Event<out Any>>): Boolean =

I was hoping something like this would work, but it's not:

if (ESEventPayload::class.java.isAssignableFrom(message.body.payloadType::class.java)) {
   println("It's using the interface")
} else {
   println("It isn't using")
}

How do I go about doing this in Kotlin?

Any help would be appreciated.

Thanks.

Answer 1

Use the is operator, which simply looks like:

if (something is ESEventPayload) { ... }

There is no reason here to use isAssignableFrom. In fact it has the negative consequence of not smart casting. When using is you can...

if (something is ESEventPayload) {
   // something here is now smart cast as ESEventPayload, no casting needed
   println(something.eventPayloadMemberOrMethod) 
} 

See: https://kotlinlang.org/docs/reference/typecasts.html