If I have: ```interface Something { fun foo(bar...

# announcements

[dave08]

If I have:

interface Something {
   fun foo(bar: Int): List<Int>
}

class SomethingImpl : Something {
   //...
}

val ref = Something::foo

and I want to invoke it, do I do this:

val instance = SomethingImpl()
ref.invoke(instance, 5)

?

[marstran]

Wow, I didn't even know you could reference a method on an interface like that, and bind it to an implementation later.

[streetsofboston]

You can rewrite ref.invoke(instance, 5) as instance.ref(5).

[dave08]

Even if the ref might be null, I could still write instance?.ref(5) ? It seems to turn out red in Intellij...

[dave08]

Even non-nullable seems to be red...

[dave08]

In my real use-case I have a list of pairs of object to funcRef NamedGroups.. and then I do:

val namedGroup = (NamedGroups.firstOrNull { it.first.id === groupId }?.second)

[dave08]

Then I do:

namedGroup?.invoke(storeRepository, user.storeId)

[dave08]

But it seems to be null for some reason...

[dave08]

Even though there is a match.

[streetsofboston]

No, for that rewrite, ref can't be null. (instance can be null, though).

[dave08]

Thanks, now it makes sense!

[dave08]

By the way, maybe it's red because the rewrite doesn't work with KSuspendFunction2? Maybe suspend functions don't support this?

[dave08]

(the ref is a suspend fun in my code...)

[dave08]

It doesn't seem to work even w/o suspend https://play.kotlinlang.org/#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

[streetsofboston]

Change the`ref` declaration:
​
val ref: Something.(Int) -> List<Int> = Something::foo
​

[dave08]

Still no go 🤕:
https://play.kotlinlang.org/#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

[dave08]

oops I forgot the (Int), it works now)... but it's funny how the same reference can be cast to both forms?

[dave08]

And that the default is the non-receiver form...

[dave08]

But thanks 😁!