the companion object of your subclass is an entirely independent object

though i’m not sure how you’d force the companion object on the subclass to do that extension.

right.

you can’t force it to do anything, and you also can’t access it from the superclass other than through reflection

my gut reaction is that if you’re trying to do that, you’re probably misusing companion objects

So I wouldn't be able to say "if you extend this class, its companion must have these functions"

you can document that...

you can't enforce it, but you can "assume" it and declare your generic methods accordingly

you can try to enforce it downstream by using functions that accept a certain interface.

I use the following pattern/idiom:

interface Foo {
    fun duStuff()
}

interface FooCompanion<T: Foo> {
    fun create() : T
}

class FooX : Foo {
    companion object : FooCompanion<FooX> {
        override fun create() = FooX()
    }

    override fun duStuff() {
    }
}

fun <T : Foo> FooCompanion<T>.doStuff() = create().duStuff()

I'll try that pattern and see how it works

I was trying a workaround with inner classes which want working

Yeah, I'll commit my changes and show the code

could you describe what you're trying to achieve?

Dang didn't mean to keep editing oops

Anyway

Basically, Channels and Groups are both a subclass of BaseChannel

All of the Slack REST API things are handled by BaseChannel, and Channel and Group just need to provide the method base for the REST API

I wanted to have the Companion Object of each class forced to have creation methods that are provided by the abstract class BaseChannel

can't you just make the methods instance methods on

BaseChannel

?

it's basicly the strategy pattern, right?

No, because then you would need a channel object to create a channel

the

fromJson

method?

All of the methods in BaseChannel.ChannelCompanion

and you need to use them outside of

BaseChannel

, right?

Yup

I think my pattern should work, then

Yeah that's what it's using now

Just with abstract class instead of interface