Is there a way to pass two functions at the same time via a lambda I have a following code

rollButton.setOnClickListener { rollDice(diceImage1)}

but want to call rollDice twice, with two different arguments e.g.

rollButton.setOnClickListener { rollDice(diceImage1) rollDice(diceImage2)}

I can't get the compiler to understand what I want to do with coerceIn

How can I query jvm system property (eg in gradle

jvmArgs "-Dfoo=true"

) from kotlin?

This

val healthBonus

inside the init block doesn't make much sense, does it?

I have a map that’s of type

VertxHttpHeaders

. That’s a type that implements

Iterable<Map.Entry<String, String>>

but it does not implement

Map

. I want to filter out some headers and get back a Map. This is what I’ve come up with:

headers
    .map { it.toPair() }
    .toMap()
    .filterKeys { noCopyHeaders.contains(it).not() }

Can I do better somehow? 🙂 I wish I didn’t have to do the two-step conversion to the map and I wish I had a `filterNotKeys`… I guess I could just add those as extensions

Something like headers.filterNot { it.first in noCopyHeaders }.toMap

Is there any convention about maximum columns like 80 or 120? I just read Coding Conventions in the Kotlin website, but it says nothing about maximum columns.

Is there a lightweight JSON lib for Kotlin? For serialization and deserialization

Could someone tell me what is the correct way to benchmark ArrayList.add(index, element) method with JMH? I made one like this but note sure if it’s the correct approach:

@BenchmarkMode(Mode.AverageTime)
@Fork(2)
@Measurement(iterations = 10)
class MyBenchmark {
    @Benchmark
    fun testMethod(): Any {
        val list: List<Int> = ArrayList()
        for (i in 0 until NR_TO_INSERT) {
            list.add(list.size / 2, i)
        }
        return list
    }

    companion object {
        private const val NR_TO_INSERT = 500000
    }
}

Any idea why this is happening when I am trying to run TornadoFX application via intellij (with Gradle) but if I am compiling the project into far-jar it's running without any issue.

Hey folks, question about

.let

and nullability. Code snippet:

val foo : String? = "sample"
foo.let { it.toUpperCase() }

Results in:

Only safe (?.) or non-null asserted (!!.) calls are allowed on a nullable receiver of type String?

I have a project that is Kotlin Backend (ktor, coroutines and kotlinx.serialization mostly) and the frontend is Vue. I would like to share some code between JS and Kotlin, especially regarding the serialization and the data classes. Can I expect being able to use a transpiled kotlin library from javascript or is Kotlin/JS only made to target directly the DOM and call other libs?

Sealed classes don't work with Lists?

class MyClass<T> {
    var prop: T = null // error
}

why does this not work? I thought that the upper bound of a type parameter is by default

Any?

Hi all, trying to set up my first ‘RecyclerView’ and a little confused as to why the View in class ViewHolder is unrecognized… noob to Kotlin and Android development, so trying to wrap my head around it

import android.view.LayoutInflater
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView

class EntryAdapter(private val context: SpeechPageActivity, private val entryList: Array<String>) : RecyclerView.Adapter<EntryAdapter.ViewHolder>() {
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): EntryAdapter.ViewHolder {
        return ViewHolder(LayoutInflater.from(context).inflate(R.layout.entry_cell, parent, false))
    }

    override fun getItemCount(): Int {
        return entryList.size
    }

    override fun onBindViewHolder(holder: EntryAdapter.ViewHolder, position: Int) {
        holder.entryText?.text = entryList[position]
        holder.itemView.setOnClickListener {
            println(entryList[position])
        }
    }

    class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {
        val entryText = view.entryText
        val entryImage = view.entryImage
    }

}

i need to use Kotlin for a technical interview, are the basic datastructures like graph and queue easily usable?

is there a one-liner for this? the bulk of the counting pairs part of the problem I mean, not the end aggregation (but also there as well)

Hey folks may I know how can we original list to another list, problem I am facing any modifcation in copied list leads to modification in original list. May I know what needs to be done in kotlin

I looked into kapt, kotlinpoet, AutoService, looked at many tutorials, but I can't get anything working unfortunately

Good day today. The KMP project we have been working on for the annual CodeWeek event is a finalist! 250 teams competing, we are one of the top 25 going into the finals in January. WatchOS KTOR client made it just in the nick of time! Still needs polishing and a good amount of refactoring, but I think the main point proven - we share logic and networking across multiple targets (and planning to add more) https://github.com/dmitrish/kinsight-multiplatform

is there a better way to write this? (less verbose and less or equal impact)

val height = points.maxBy(Point::y)!!.y - points.minBy(Point::y)!!.y

I often find myself using this schema

val height = points.map(Point::y).run { max()!! - min()!! }

uses less characters but iterates an additional time through

points

of course if i really wanted to do it best by performance, i could accomplish this in only one iteration...

hi all,, is there any method which convert list to int separate with ” , ” likes

joinToString()

I means

val list = listOf(1,2,3)

// i want the result like this
// 1,2,3 <= each is int value

Is it okay to nest sealed classes. So UserData is a part of ModelData, but UserData can also have its own hierarchy with two separate types of UserData, in this case LoginData and AuthenticationData. Or is there any better solution for this?

So, I have a bunch of data immutable classes that make up a nested structure (represeting a GraphQL response) and I'd like to mutate one of the nested values to get an immutable copy. for example:

data class User(val name: String, val location: Location)
data class Location(val city: City, val somethingElse: String) // for example
data class City(val name: String, val country: String)

I have a user and I want to change the city name, getting a copy of user with everything else on the chain unchanged. I can do it with copy:

val newUser = user.copy(location = user.location.copy(city = user.location.city.copy(name = "New name")))

but that's far too long esentially I'd like to be able to do something shorter like:

val newUser = user.copy { it.location.city.name = "New name" }

I don't think the above could get gotten to work, but is there something in those lines I can do? (also, not my actual data structure, but sufficient for this example) Thanks 🙂

When you create default project there is the following in

build.gradle

:

jvmJar {
    dependsOn(jsBrowserWebpack)
    from(new File(jsBrowserWebpack.entry.name, jsBrowserWebpack.outputPath))
}

How do you express that in

build.gradle.kts

? Probably, I've got a part of this right, but I'm not sure about the last expression

tasks.named("jvmJar") {
    dependsOn("jsBrowserWebpack")
}

Hi there #getting-started which IDE should I use for kotlin+android development 🙂

hi guys i know how to print all of array element in one line

val topStudents = arrayOf("Jake", "Jesse", "Matt", "Alec")
names.forEach { println(it) }

but how to do in this condition.

val allStudents = setOf {
      "Michael",
      "Kim",
      topStudents <= i don't know how to retrieve topStudent each names likes "Michael" and "Kim" 
}



// the result what i want is 
val allStudents = setOf {
      "Michael",
      "Kim",
      "Jake",
      "Jesse",
      "Matt",
      "Alec"
}

can someone help me with generics? lets say I already overload

Number

operators and now I want make generics

Point

that will also overload operators based on

Number

, f.e result of

Point<Float> + Point<Float>

should be

Point<Float>

but recently is

Point<in Float>

:<

data class Point<Unit : Number>(val x: Unit, val y: Unit, val z: Unit) {
  operator fun plus(increment: Point<Unit>): Point<in Unit> {
    return Point(x + increment.x, y + increment.y, z + increment.z)
  }

  operator fun minus(increment: Point<Unit>): Point<in Unit> {
    return Point(x - increment.x, y - increment.y, z - increment.z)
  }

  operator fun times(increment: Point<Unit>): Point<in Unit> {
    return Point(x * increment.x, y * increment.y, z * increment.z)
  }

  operator fun div(increment: Point<Unit>): Point<in Unit> {
    return Point(x / increment.x, y / increment.y, z / increment.z)
  }
}

Is there any difference between nested sealed sub-classes and not nested sub-classes except for the way sub-classes are accessed?