Hello Word I was wondering if there s any way to craft a Jav kotlinlang #announcements

Hello, Word! I was wondering if there's any way to craft a Java method in such a way that it can be called in Kotlin like a "function literals with receiver". So I could call

myObj.foo { bar() }

where

bar

is a method on some class passed as the receiver of the lambda - but

foo

is declared/implemented in Java. Ideas? 🙂

Andreas Sinz

12/02/2018, 4:52 PM

I don't think that is easily possible, why do you need that?

bod

12/02/2018, 4:53 PM

it's just that I make a Java library, but I want it to also be Kotlin friendly

twisterrob

12/02/2018, 4:53 PM

wouldn't it be possible to write in Kotlin? As Java users can still call those methods

receiver is a concept in Kotlin, even if it's possible, you'll probably need some Kotlin annotation from stdlib, so you might as well declare the surface API in Kotlin

bod

12/02/2018, 4:54 PM

hmm that's true but then I need to make it depend on the Kotlin stdlib - and since it's a small library that's a bit "too much"

twisterrob

12/02/2018, 4:56 PM

you can try to see what metadata annotations are attached when declaring a lambda with receiver in the class files and mimic that from Java, I never tried to hack around with this yet.

javap

will be your friend

bod

12/02/2018, 4:56 PM

I guess I could just add extensions to a kotlin specific optional dependency.... 😛

twisterrob

12/02/2018, 5:00 PM

yeah, that's what everyone does 🙂

be careful with overloading a member from an extension; member always wins; if it doesn't work you may need to introduce a new name for kt

bod

12/02/2018, 5:02 PM

oh thanks for the tip! 🙂

twisterrob

12/02/2018, 5:03 PM

https://github.com/JetBrains/kotlin/blob/master/spec-docs/NameResolution.adoc is a fun read 🙂

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