How to check whether the type of objects inside a

List<*>

is a kotlin official class or my own class, I currently check its name:

paramName.substring(24).removeSuffix(">")

, so

"kotlin.collections.List<nz.salect.objJSON.Lesson>"

will become

"nz.salect.objJSON.Lesson"

, and then I can verify whether it

startsFrom("kotlin")

or not. What’s a better way to do this?

@udalov Thanks! I solved this via this

param.type.arguments[0].type?.classifier as KClass<*>

Beware of the fact that type's classifier may not be a class, e.g.

fun <T> foo(): List<T>

here

List<T>

is a list of

T

, which is not a

KClass

and therefore will crash with ClassCastException

@udalov Thanks for the reply, do you mean that I should try catch this

as

cast to handle the potential

ClassCastException

?

No. It's never a good idea to catch

ClassCastException

. What I'm saying is that if this situation (type variables) is possible in your use case, you should handle it by inspecting the type of the returned classifier.

KType.classifier

returns

KClassifier

, which has exactly two subclasses:

KClass

and

KTypeParameter

. So if this is possible in your use case, you should have code like

val type = param.type.arguments.first().type
when (type.classifier) {
    is KClass<*> -> ...
    is KTypeParameter -> ...
    else -> throw UnsupportedOperationException()
}

Or, a completely different approach, which I suggested in another thread, is to use

jvmErasure

which always gives the

KClass

but loses type information about generics which might be valuable in your use case (again, I don't know what you're using this for, but it might be better one way or the other)