Given a sealed class Foo and an instance of `val someClass: KClass<out Foo>` is it possible fo...

# announcements

[pajatopmr]

Given a sealed class Foo and an instance of val someClass: KClass<out Foo> is it possible for someClass.objectInstance to be null? I think the answer is yes but I am struggling to come up with a way to make a test for such a thing. The documentation for objectInstance says, ” …if this class is not an object declaration” so my question really boils down to: how do I define a class that is not an object declaration? And the corollary, can I define a member of a sealed class that is not an object declaration. If you’re inclined to reply, please do so in a thread. Thanks. fwiw, my brain hurts just trying to grok this.

[Pavlo Liapota]

I have a guess that singleton declaration:

object Bar {
    // ...
}

is object declaration.
And usual class declaration:

class Bar {
    // ...
}

is not.

[pajatopmr]

@Pavlo Liapota your analysis makes sense to me but seems to be opposite to the documentation: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.reflect/-k-class/object-instance.html

[pajatopmr]

I will run this through the debugger to see what it says …

[pajatopmr]

And the debugger says the documentation is correct. Boy am I confused.

[pajatopmr]

So I clearly misunderstood what objectInstance provides. I thought it gave an instance for the receiver (a KClass) but not the case. Next question is, how does one get an instance from a KClass? I will be researching that but feel free to shortcut my effort. 🙂

[Pavlo Liapota]

Do you want to create a new instance by KClass using default constructor?

[pajatopmr]

I know how to do this with the JVM but not with Native or JS. Being able to create a KClass instance multiplatform would be nice. If you know how to do that I am all eyes. 🙂