kotlinlang #getting-started

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getting-started

kotlinforandroid

06/30/2022, 11:54 AM

I have an annotation where I want to be able to reference Android Compose ImageVectors using a field. For example

annotation class Ref(val icon: ImageVector)

Is this somehow possible to accomplish? I guess I can use

KClass<out ImageVector>

but I do not really understand how that would interact since all material icons from compose are defined as `val Icons.Filled.Add`for example.

smit01

06/30/2022, 11:57 AM

will Kotlin-Conf23 Amsterdam workshop and talk videos be available on Kotlin official YouTube channel for students like me who can not afford to travel at moment?

👍 3

hfhbd

07/01/2022, 7:15 AM

If you use a ReadWriteProperty with the by operator, is there any possibility to access the underlying delegate? Ideally, I want to override the toString method but keep using idiomatic code

Klitos Kyriacou

07/01/2022, 4:45 PM

I have a use case for a

Map<Int, String>

. Each map has only a small handful of entries. I need to keep many thousands of these maps in memory. 99% of the time the

Int

key is small, between 1 an 10. If it was guaranteed to always be that small, the most efficient implementation of such a map would use an

Array<String?>

. However, 1% of the time there would be a key that would be a very large integer, so a simple array is unusable. Yet if I use a

HashMap

TreeMap

I would be wasting memory for 99% of the time by using a sub-optimal implementation. Is there any specialized Map that uses a strategy of changing internal implementation depending on the value of the key?

julian

07/01/2022, 10:13 PM

A function reference passed as an argument to an inline function will not be inlined. Is that correct? That's what it looks like from the bytecode, but I'm on shaky ground when making sense of bytecode.

Hassaan

07/02/2022, 12:33 PM

Isn’t ‘protected’ has lesser visibility than ‘internal’ ? Then why following:

oday

07/02/2022, 4:13 PM

so if I’m using Kotlin 1.7.0, does “K2” come included or something? how do I enable it, how do I try it?

Loney Chou

07/04/2022, 5:28 AM

Is it possible to generate overriden methods from java which have non-null parameters by default? Right now it always marks every parameter as nullable if is not primitive.

Pablo

07/04/2022, 7:23 AM

Hello how can I update a list for instance. I have this

fun getList() : List<Foo>

val myList = getList()

Now I want depending on my flag sort or not that list, I've tried it but did not work

val myList = getList().apply { if(bar) mySorter.sort(this) }

Is there any kotlinian way to sort the list instead of creating a new val?

reactormonk

07/04/2022, 9:26 AM

Can I have an

enum class

with an "other value"? Aka

enum class Status(val value: Int) {
  Present(2),
  Absent(1),
  Error(value)
}

reactormonk

07/04/2022, 1:47 PM

x and 0xFF.toByte()

a noop? Aka

x and 0xFF.toByte() == x

is always true?

Andrew Cerne

07/04/2022, 3:14 PM

👋 Hello, team!

👋 4

👋🏼 1

reactormonk

07/04/2022, 4:50 PM

How would y'all represent bit fields? Aka convert them to the

Byte

to send them to the wire and back, and preferably a reasonable API along the way.

Chris Fillmore

07/04/2022, 8:23 PM

Is it safe to cast

T & Any

reactormonk

07/04/2022, 8:54 PM

What's the syntax for two bounds in generics?

fun <A: Enum<A>, Positional> EnumSet<A>.toByte(): Byte {

Apparently it's not

nor

Alan B

07/05/2022, 1:56 PM

I swear I have long covid and brain fog or something. Is there an idiomatic way in Kotlin to

map

while supplying the map-like operation with a list of functions (or vararg) to apply to each element, rather than a single transformation? basically ~~collection.mapAll(transformers: List<(T) -> R>)~~

sequence.mapAll(transformers: List<(T) -> T>)

I want to supply a list of transformers so I don’t have to do something like:

sequence.map(::first)
.map(::second)
.map(::third)

would be:

sequence.map(tranformers)

Marcus Brito

07/05/2022, 2:29 PM

hey guys — is there any way I can keep a data class property declared as

Long

exposed as a boxed

java.lang.Long

, as opposed to a

long

primitive? Other than making it nullable, that is.

reactormonk

07/05/2022, 2:43 PM

How do I write tests? Do you use https://kotlinlang.org/api/latest/kotlin.test/ ? There's no doc linked form there? 🤔

Pascal Gerrist

07/05/2022, 3:19 PM

Hey folks! Does anyone have experience with SimpleXML? I'm trying to parse XML into an object but getting some errors.

nkiesel

07/05/2022, 7:25 PM

I recently (my guess is: after upgrading to Kotlin 1.7.0) have issues with IntelliJ not seeing Java changes in my Kotlin code. Concrete example is that I had a simple Java pojo with a default constructor which was called from Kotlin. I now added a second constructor and changed the Kotlin code to use that. That does compile and works, but IntelliJ shows an "Too many arguments for public constructor" error. I guess invalidating caches and restarting IntelliJ will fix this, but that is of course cumbersome. Is that a known issue?

Monroe Walker

07/05/2022, 10:16 PM

Hey! I asked this on the forum already: https://discuss.kotlinlang.org/t/compilekotlin-execution-time-seems-to-randomly-vary-within-2-10-second-range/25154/2 but am also asking here in case people check this more often - my compileKotlin step of my gradle build varies in execution time within a window of about 2-10 seconds. I'm trying to figure out why it takes longer when it does but I'm not sure what to look into. Any advice?

Erik

07/06/2022, 3:06 PM

(If wrong channel, let me know!) If a function has multiple arguments, e.g.:

fun f(x: Int, y: Int) = TODO()

then it is possible to autocomplete them with arguments like so: Type:

, then it should suggest to autocomplete

and then you press some key so that the IDE (Android Studio or IntelliJ) now completes it to

f(x = , y = )

, with the cursor just before the comma so you can continue typing, e.g.

and then you press tab to move the cursor to the next argument (

y =

) so you can continue typing. I'm sitting right next to a colleague who can do this in one project. But not in another, so we think it's a project setting that's somehow enabled in one project, but not in the other. This would be super helpful to enable this in all our projects, but how do we do that? What's this feature called? Is there a keystroke to use? Is this something that can be enabled?

Sangeet

07/06/2022, 3:30 PM

Any idea why lint or kotlin compiler is not showing error for below code

fun <T : CharSequence> doSomething(): T {
    return String() as T
}

class Something(intValue: Int)

Something(doSomething()) // Doesn't show any compile error

It seems that it is automatically casting CharSequence to Number and throwing error in runtime.

Monroe Walker

07/06/2022, 6:01 PM

Does Kotlin DSL offer a way to require a pattern for strings to follow? Either by regex or some validator function?

allan.conda

07/07/2022, 4:27 AM

is there a way to cache the map function of a flow for distinct events so it doesn’t recompute for the same value?

flow(1, 1, 2, 2, 3).map { expensiveMapping(it) }.collect()

Colton Idle

07/07/2022, 4:07 PM

Not sure if this is the right spot, but is there a reputable library for Kotlin for public key RSA encryption? I just need to encrypt a string. My iOS team is using https://github.com/TakeScoop/SwiftyRSA but i cant find something like that for kotlin.

Will_505

07/07/2022, 7:26 PM

Hey! I have come across an error in the IntelliJ IDE in Main.kt the tutorial i am following is telling me to declare my functions like so but i am getting issues with the compiler. the code:

fun sayHello(itemToGreet:String) = println("Hello $itemToGreet")

fun main() {
    sayHello(itemToGreet: "Kotlin")
    sayHello(itemToGreet: "World")

}

The error:

Alex Stelmachonak

07/08/2022, 1:18 AM

Hi. Something strange happening to my gradle (groovy) project when trying to update kotlin version from 1.6.21 to 1.7.10:

An exception occurred applying plugin request [id: 'org.jetbrains.kotlin.jvm', version: '1.7.10']
> Failed to apply plugin 'org.jetbrains.kotlin.jvm'.
   > The task 'compileKotlin' (org.jetbrains.kotlin.gradle.tasks.KotlinCompile) is not a subclass of the given type (org.gradle.api.tasks.compile.AbstractCompile).

* Try:
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights.

* Exception is:
org.gradle.api.plugins.InvalidPluginException: An exception occurred applying plugin request [id: 'org.jetbrains.kotlin.jvm', version: '1.7.10']
	at org.gradle.plugin.use.internal.DefaultPluginRequestApplicator.exceptionOccurred(DefaultPluginRequestApplicator.java:223)

Looks like something simple, but as often with gradle, simple things are not simple to find 😞 Any ideas anyone?

reactormonk

07/08/2022, 9:56 AM

How come the IDE complete

CardStatus.Companion.Present

instead of

CardStatus.Present

here?

sealed class CardStatus(val value: Int) {
    companion object {
        fun fromInt(int: Int): CardStatus {
            return when(int) {
                255 -> PowerSavingMode
                3 -> Powered
                2 -> Present
                1 -> Absent
                else -> Error(int)
            }
        }

        object PowerSavingMode: CardStatus(255)
        object Powered: CardStatus(3)
        object Present: CardStatus(2)
        object Absent: CardStatus(1)
        data class Error(val errorValue: Int): CardStatus(errorValue)
    }
}

Slackbot

07/08/2022, 10:35 AM

This message was deleted.