Is there a "clean" way to enforce an exhaustiveness check for

when(someSealedClass)

? I just came across a piece of code where it was very natural to use then

when

without any assignment, hence the compiler would never complain when a branch was missing 🤔

What is the recommendation to use/not use "this" in an extention function, because in many cases it could be ommited? I read the Kotlin style guide and didn't find any information about it.

The pattern Singleton in Kotlin is designed by object, so if in java to get an instance of the singleton while we create it : public static SingletonClass getInstance(param1, param2, ...) which will initialize some var "Dynamicly" in the SinletonClass and in the same time create the instance using this params, and as we know there is no constructor in kotlin objects, so how do i pass my params to the object dynamicly ?

is there a way to disable the warning, that inlining some function will have a negligible impact on the performacne? I'm using it sometimes because i want the code RIGHT THERE or because the function is empty and don't do it for performance

I try to use MPP. And I have several JS targets, so my common sourseSet use JS specific code too. But IDEA don't recognise those common source sets as JS-specific. Is there any solution to work in IDEA with such project?

Kafka has this interface which "gets" a

Processor<K,V>

public interface ProcessorSupplier<K, V> {
    Processor<K, V> get();
}

Given I have a class:

class EventNotifier : Processor<String, SomeEvent>`

I thought I'd be able to call the

Kstream#process(ProcessorSupplier<? super K, ? super V> var1, String... var2)

method, but I am getting a type mismatch error for:

stream.process({ EventNotifier() })

Join #wwdc if you’re watching, let’s chat 🙂

Can I make Kotlin recognise that

java.io.File.listFiles

returns null sometimes?

Is there a reason this doesn't function in this way?

why is the

Result<T>

shouldn’t be a return type although

runCatching

does?

Hey is anyone here doing Kotlin contract work?

Does Kotlin have a release schedule ? e.g. what is approx release date of 1.4 ?

Is this a compiler bug or am I missing something?

abstract class A<T> {
    abstract fun broken(vararg values: T): T
}

// Error: Class 'B' is not abstract and does not implement abstract base class member public abstract fun broken(vararg values: Int): Int defined in A
// Error: 'broken' overrides nothing
class B : A<Int>() {
    override fun broken(vararg values: Int): Int {
        return 5
    }
}

The same code works fine if the subclass is with a "normal" object and not a primitive type. Actually the IntelliJ IDE also thinks it should work, at least it generates the code for it but the compiler then complains about it. Tested with kotlin 1.3.31

is kotlinx.serialization works on java classes ?

Can i combine varargs with lambda? It seems its not possible to define a varargs in kotlin, am i missing something for example

val varArgsFunction = createVarArgsFunction("foo")
varArgsFunction(1, 2, 3)

Can a non-null property have a nullable field?

Can anyone explain how CursorAdapter is closely coupled to Activity

If you are in a function in a supertype and have a variable that is of that type but then smartcasted to a subtype, why do the private functions of the supertype get hidden?

What’s a clean and short Kotlin way to pipe from a BufferedReader into a BufferedWriter?

Can anyone recommend beginner-friendly open source Kotlin projects?

Hi, TypeScript uses the same convention to describe constraints for generic types for both classes and functions e.g.

function foo<T extends Bar>() {}

and

class Foo<T extends Bar> {}

. Just out of curiosity were there any limitations why it couldn't be like

fun foo<T : Bar>() {}

in Kotlin?

i have a

data class

which has a property of type Array<String> (let's forgo discussing whether or not to use arrays at all). Let's do a step back: What should the

equals

method generated for data classes do? I think they should compare the values of data classes. Unfortunately when the

data class

has an

Array

property compares those arrays using

equals()

and not using

content(Deep)Equals()

. Do you think this is a good idea? why?

See the appendix of https://blog.jetbrains.com/kotlin/2015/09/feedback-request-limitations-on-data-classes/

hi, do we have a coroutines channel? thank you.

@thana I submitted a feature request for allowing to explicitly request use of

contentEquals

a while ago: https://youtrack.jetbrains.com/issue/KT-26499 You can add your vote.

For example: if this directory had these classes:

class Foo {
   fun bar() {
        println("bar")
   }

   internal fun bar2() {
        println("bar2")
   }
}

internal class Foo2

It might output something like:

// public_api.txt
class Foo {
   fun bar()
}

How many full time devs does JB have on Kotlin?

I have a use case that is causing some trouble. We have an interface:

interface Foo<T> { 
   fun bar(t: T)
 }

And we want to be able to have the same interface but without the parameter:

interface Foo {
    fun bar()
}

but this is not possible because we are redeclaring the interface name. A possible solution is to declare

Foo<Unit>

and pass

Unit

instead of having the second interface without parameters, but this verbose on the calling and declaration site. We have an extension function

fun Foo<Unit>.bar() = bar(Unit)

to make the calling site clearer, but declaring it is still a little bit cumbersome. Any ideas on how to achieve this?

anything convenient to convert a kotlin list to a java list?

to pass as argument to jdbc for example