kotlinlang #getting-started

I vaguely remember something about there being defined time periods between Kotlin releases (maybe it used to be here ). Is that accurate, or is there no guaranteed time between releases?

Kenneth

11/10/2021, 2:28 PM

How do people do wsdl to kotlin?

Nikolay Lebedev

11/10/2021, 7:53 PM

How can I create a class that takes a string and any other serializable class and has a method to return itself serialised into json encoded as string?

Richard Gomez

11/10/2021, 8:49 PM

Is there any documentation that clearly explains the difference between Kotlin's

Regex

vs. Java's

Pattern

11/11/2021, 2:48 AM

Hello, I'm to new to kotlin in general, and I love it. I'm intending to create an application for my personal use (finance), what is the recommended GUI library that I should use? I'm mainly going to use it on windows (so other platforms do not matter that much), and what kotlin platform should I use? (or learn?) or should I wait for the libraries/native/multiplatform support to get more stable before developing the application?

Erik Bender

11/11/2021, 8:14 AM

Hi 🙂 I have this function to deserialize generic lists from

ByteArray

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fun mapBytesToList(arr: ByteArray): List<T> {
  if (arr.isEmpty()) {
    return emptyList()
  }
  val bais = ByteArrayInputStream(arr)
  var ois: ObjectInputStream? = null
  return try {
    ois = ObjectInputStream(bais)
    ois.readObject() as List<T>
  } catch (e: Exception) {
    emptyList()
  } finally {
    try {
      ois?.close()
    } catch (e: Throwable) {
    }
  }
}

I get a

UNCHECKED_CAST

warning at

ois.readObject() as List<T>

. Do you have a hint on how to improve this function?

Sivan

11/11/2021, 9:25 AM

Is it possible to add a kapt to the dev variant build only? Have to add a kapt for jdbc processor but we want to keep it only on our dev builds. Possible?

Marko Kunic

11/11/2021, 9:51 AM

is there a way to enforce ktlint checks in gradle build? eg. I run build or tests, and it fails because style isn't correct

Zode

11/11/2021, 9:56 AM

Is xcode13 compatible yet？ I got an error when trying to build K/N

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FAILURE: Build failed with an exception.

* Where:
Build file '/Users/xxxx/Develop/kotlin/kotlin-native/build.gradle' line: 66

* What went wrong:
A problem occurred evaluating project ':kotlin-native'.
> Incorrect Xcode version: 13.1. Required major Xcode version is 12.

Guru

11/11/2021, 5:54 PM

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fun main() {
    val callback = { i: Int, j: Int ->
        val ii = i.times(j)
        val jj = j.times(ii)
        ii + jj
    }

    println(addAndMultiply(5, 6) { i, j ->
        i + 1 + j
    })

    println(addAndMultiply(5, 6, callback))
}

inline fun <T> addAndMultiply(x: T, y: T, call: (T, T) -> T): T where T : Number {
    if (x is BigDecimal || x is BigInteger) return call(x, y)
    if (y is BigDecimal || y is BigInteger) return call(x, y)

    return call(x, y) * x * y
}

I am getting reciever type mismatch at

return call(x, y) * x * y

Any Idea ?

martmists

11/11/2021, 7:24 PM

Where should I go if I get this error?

org.jetbrains.kotlin.backend.common.BackendException: Backend Internal error: Exception during IR lowering

Platform is JVM, and it seems like it has to do with my suspend functions

martmists

11/12/2021, 1:58 AM

Implementation detail: If I write an extension function like so:

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val Extension.dispatcher by lazy {
    SomeDispatcher()
}

Will the

dispatcher

property be different for every Extension or will there be one global dispatcher

Simon Lin

11/12/2021, 7:58 AM

How to flatten a list that deep layer is not same: ex1:

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val deepList = listOf(
    listOf(
        listOf(-1, 0),
        listOf(1)
    ),
    listOf(2, 3),
    listOf(4, 5, 6)
)
println(deepList.flatten()) // [-1, 0, 1, 2, 3, 4, 5, 6]

ex2:

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val deepList = listOf(
    -1,
    listOf(listOf(listOf(0))),
    listOf(2, 3),
    listOf(4, 5, 6)
)
println(deepList.flatten()) // [-1, 0, 1, 2, 3, 4, 5, 6]

Pavel Repkin

11/12/2021, 11:21 AM

Hi! I don’t see a multiplatform channel. Where should I ask questions on multiplatform development?

Moritz Post

11/12/2021, 11:30 AM

hello i have a list of numbers in the range 1-255. how could i transform these numbers into a

ByteArray

? a direct conversion via

byteArrayOf

does not work since the numbers are unsigned but

ubyteArrayOf

does also not work for a reason i don't fully understand. It would be possible to map each number to

it - 128

but that seams a bit unefficient. Help would be appreciated.

Tomas Kormanak

11/12/2021, 12:13 PM

Is there some function like

with

which is ignoring return value and returns

Unit

? Something like this:

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public inline fun <T> with(receiver: T, block: T.() -> Unit): Unit {
    receiver.block()
}

Or any better idea how to avoid explicitly returning Unit in this case:

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fun process(data: Data) = with(data) {
    ///doSomething
    Unit
}

Matias Reparaz

11/12/2021, 1:18 PM

Hi, I have an interface with a method like this

fun doSomething(param: SomeParams): Single<Something>

where Single is from RxJava. I want to use coroutines inside my implementation and wrap the value at the end. But how can I create the CoroutineContext? It’s ok to use the runBlocking in this context? something like this:

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fun doSomething(param: SomeParams): Single<Something> = Single.just(
   runBlocking {
        doSomething()
    }
)
suspend fun doSomething(): Something = TODO()

Thanks

mcpiroman

11/13/2021, 11:58 AM

Is there a shorter way to write:

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val rng = Random(0)
generateSequence { rng.nextInt() }.take(10).toList()

Danny Morgan

11/13/2021, 12:41 PM

https://play.kotlinlang.org isn't working for me since yesterday afternoon (12 Nov)... Anyone have information about this? (specifically, even with hello world example at start; it returns errors) (update) an issue has been filed https://youtrack.jetbrains.com/issue/KT-49687

✅ 1

dave08

11/14/2021, 10:57 AM

Given:

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class Foo(val bar: Bar)
class Bar(val baz: String)


val foo = Foo(Bar("baz"))

// why isn't this possible?
val bazGetter = Foo::bar::baz

// whereas this is ok?
val bazGetter2: (Foo) -> String = { it.bar.baz }

reactormonk

11/15/2021, 11:52 AM

Is there a way to figure out where something's being constructed in a project with a whole lot of javax

@Inject

flying around? Or what's the usual way to extract parts of the codebase and sending a few arbitrary values through it for exploration purposes? I feel like I'm trying to fight the structure of the codebase here if I'm trying to construct everything manually.

Mendess

11/15/2021, 12:10 PM

How do I know if a lateinit local variable is initialized?

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fun foo() {
    lateinit var x: Int
    if (::x.isInitialized()) {}
}

This doesn't seem to work

Ayfri

11/15/2021, 2:45 PM

Hi, I have two numbers that are random, can be negative, first can be above second or not or even equal. I want to create a range between these two numbers that always have a step of

and start always at the lower number, how can I do it in a simple way ?

Bernhard

11/15/2021, 2:52 PM

Hi, I've got a data class but in one case I want one attribute of it to be evaluated again on each access (getting the current date basically). How do I do this?

Steve Kim

11/15/2021, 4:58 PM

Hi, We have officially released 5 kmm libraries. https://twitter.com/LINE_DEV_EN/status/1456180731965706248?s=20

eygraber

11/16/2021, 4:00 AM

Is there a "kotlin" way to do something like

Scanner(myFile).findAll(myPattern)

that returns a `Sequence<String>`(I know I can call

asSequence

on the returned

Stream

but I'm wondering if there's a specific Kotlin API for that)?

ankushg

11/16/2021, 7:52 AM

Doing a cleanup of a codebase and marking some stuff as

@Deprecated

A couple pain points that are popping up: 1. Deprecated code tends to call other deprecated code, and this generates too many warnings. I currently have a ton of

@Suppress("KotlinDeprecation", "DEPRECATION") @Deprecated

declarations all over my codebase, when there are only one or two actual places that are using the top-level, public Deprecated method. 2. Deprecations in
import
statements are tricky. When I intentionally use a deprecated declaration, I can

@Suppress

it at the call site. But I can't

@Suppress

the warning I get just for importing it! For top-level declarations, I can use the fully-qualified name everywhere and just avoid importing the deprecated declaration. This doesn't work when you're using an extension function contained in an

object

though. Questions: • Is there a way to automatically suppress Deprecation warnings within declarations that are also Deprecated? • Is there a way to get the compiler to ignore when a

@Deprecated

declaration is imported, but still warn when it is used? • Or alternatively: is there a way I can use a fully-qualified name to avoid importing an extension function contained in an

object