Different question: I want to return 1 if a map's value is not set or am empty list. Is there a more elegant way than:

if (!myMap.containsKey(color) || myMap[color]!!.isEmpty()) return 1

Can I deconstruct variables while assigning them? Works:

var (a ,b) = somethingReturningAPair()

But what does not work:

var a: Int
var b: Int
(a, b) = somethingReturningAPair()

Or does it only work when initalizing variables?

heyo! new to the server, but i've been using Kotlin since alpha koans. i was directed here while doing some research into Desktop Compose.

Hi as an android developer is it good to know only flutter ?

Trying to create a list of unique numbers. Why is this statement not working?

mineLocation = Set<Int>(mineCount) { Random.nextInt(0, length * width)}

I have a fonction that builds a data class out of a JSON response from an API. Until then, that is fine. But when I have pagination, I don’t know how to generate a unique data class from the different pages. Can we “merge” 2 data classes? I’ll probably end up handling a list of Data Classes (which will impact a lot the rest of the code) but if anyone has an elegant idea ... 🙂

Noob question. I'm using Android Studio (android development) I've Included dependencies:

implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.4.2"

But I cannot use

async

and

launch

in a

suspend fun

suspend fun foo() {
  async {} // Unresolved reference
  launch {} // Unresolved reference
}

What am I missing here?! EDIT: nevermind, I was remembering it wronly, I need something like

coroutineScope {}

or

withContext(...)

or something like that

👋 ¡Estoy aquí! ¿Qué me he perdido?

Hey i made an Annotation Processor in Java now I want to use them also in Kotlin, but the doesnt work. What can I change in the annotationprocessor so that it also works with kotlin?

Hi lovely people! I am interested in developing Kotlin Multiplatform Applications. I have read through the docs and I can't exactly pinpoint what the differences are between Kotlin Multiplattform and Kotlin Multiplatform Mobile

For example, the docs for Kotlin Multiplatform list IntelliJ IDEA as a possible IDE you could use, but the KMM docs only mention Android Studios (for the backend atleast)

if

Path

is now the preferred way over

File

in Java, why is there no

readBytes()

extension on

Path

?

I'm trying to use

MutableStateFlow

for the first time, but it is not doing what I expect

private val state = MutableStateFlow<MyState>(INITIAL_STATE)

suspend fun refresh(): MyState {
  val newState = service.refresState()
  this.state.value = newState
  return newState
}

fun observeState(): Flow<MyState> {
  return state
    .transform { s ->
        if (s !== INITIAL_STATE) {
            emit(s)
        } else {
            refresh() // expecting this to automatically send a new state to the flow
        }
    }
}

I was expecing the

refresh()

to cause a new state to be emitted, but it didn't. Can someone guide me in the right direction? thanks.

Using coroutines what is the proper way to launch/execute multiple independent blocks in parallel? for example

for taks in tasks:
launch { task }

or would it be something like:

launch { task1, task2, ..., taskN }

Can somebody spot what's the problem I'm always getting null using this regex:

val output = (...)
 
 """public \w*\s*class (.+)\.(\w+) \{\n([^\}]*)\}$""".toRegex().find(output)

Here's the thing to match against:

Compiled from "Test.kt"
public final class com.github.animeshz.keyboard.jni.Test {
  public final native void test(kotlinx.coroutines.flow.Flow<java.lang.Integer>);
  public com.github.animeshz.keyboard.jni.Test();
}

Seems that regex is correct according to this https://regex101.com/r/PEv4BL/2

Hi, I need to use this format

32 + 64 + 4 + 128

. The problem is that I don't want the numbers to be added up. If I use quotation marks to turn it into a String, I get an error because the method needs Ints. Any ideas?

How do I make

Flow.transformLatest()

complete when upstream completes?

upstream
  .transformLatest { state ->
    emitAll(dataForState(state))
  }

say upstream is

currentState
  .takeWhile { state -> isCloseNowState(state) }

This would be easy if I had control of it, I could use

transformWhile

, what if I don't? How do I cancel

dataForState

when upstream completes? Actually, this is challenging even when I use

transformWhile()

cause it is not cancelling the previous one I'd need a

transformLatestWhile

I’m having a small issue that is confounding me. I’m trying to gather my validation messages inside a class’ companion object like so:

internal companion object {
        internal val validation = object {
            val name_blank: String = "Presenter must have a name"
        }
    }

The problem I’m having is that the name_blank property is not visible anywhere.

Presenter.validation.name_blank // Error, name_blank not resolved

if you have a static java method like:

public static <T> MyFactory<T> of(Class<T> baseType) { ... }

and you wanted to write a kotlin extension method like:

fun <T> MyFactory<T>.withSubTypes(types: List<Class<T>) {
   var factory = this
   types.forEach { factory = factory.withSubType(it) }
   return factory
}

How do you properly type the static method? If you write something like:

val factory = MyFactory.of(MyClass::class.java)
              .withSubTypes(listOf(...))

You'll get a syntax error on your list:

Type mismatch. Required: Nothing Found: MyClass

. Adding explicit type arguments doesn't help.

I have a small problem to solve. I need a data structure similar to map but it only allows to assign value the first time. I understood that I could create a customise Map class but I am looking for a shorter way from built int library. Ex:

m = mutableMapOf<String, Int>()
m.put("a", 1)
m.put("a", 1) // throw exception here

What is the best way to read from files without going through Java.io.File?

Im just starting out with coroutines, so this may be a weird question. Is it possible and how would I go about implementing a

MainCoroutineDispatcher

that simply runs the coroutines on an existing main thread?

Hi there. 👋 I recently wanted to implement a generic interface with Comparable constraint for all numbers, but found that the Number class does not implement the Comparable interface. Are there any reasons for such behavior? All implementations (Double, Byte and etc) implements the Comparable interface (and can be compared to any of numbers except Char) and in general all numbers can be compared (and also used in basic math operations). Maybe it makes sense to make Char comparable with any number and add default Comparable implementation to Number or exclude Char from Number because it does not support basic numeric operations?

Is the following statement correct?

In Java, arrays store primitive types whereas collections store boxed types. In Kotlin, both arrays and collections store boxed type whereas one can use classes like

IntArray

,

ByteArray

, etc. to store primitive data type without boxing.

One would use

intArrayOf()

if one wants to initialize an

IntArray

with specific and different values otherwise one can simply use

IntArray()

. Is that correct?

* These two are the same

val arr: IntArray = intArrayOf(0, 0, 0)
val arr = IntArray(3)

* IntArray with different values

val arr = IntArray(3)
arr[0] = 1
arr[0] = 2
arr[0] = 3

vs

val arr: IntArray = intArrayOf(1, 2, 3)

Given this enum class:

enum class Trait(code: String) {
        AMBITIOUS("ambitious"),
        HUNTER_1("hunter_1"),
        WRATHFUL("wrathful"),
        CALLOUS("callous"),
        VIKING("viking"),
        EDUCATION_MARTIAL_3("education_martial_3")
    }

I want to access the

code

property as described in this tutorial: https://www.baeldung.com/kotlin-enum Having this statement

val code = Trait.EDUCATION_MARTIAL_3.code
                                    ^^^^^

Where

code

Unresolved reference: code

Was the feature removed from the latest Kotlin version or what happened?

Hi, I am using a View Model to pass some values based on user clicks. It is working great apart from one thing: my initial default Int in the View Model cannot be 0, because if I use 0, the app resets when I first open it and click on a button. For my initial value I need this code:

val notificationManager: NotificationManager =
        context.getSystemService(NOTIFICATION_SERVICE) as NotificationManager

But I read that using a context in a View Model is the wrong approach. Is there a solution to this?

Hi, quick question about doubles. In Kotlin,

0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 < 0.8

evaluates as true, because the left-hand side is actually 0.79r instead of 0.8. What's the best way of dealing with this? I guess I could convert to a string and back, but that feels a little 'hacky'. Is there a better way?

I have a list of numbers:

val numbers = listOf(1,0,4,0,10,14,16,0,0,34,46)

how can I transform it in another list where each number is the maximum so far?

val numbers = listOf(1,1,4,4,10,14,16,16,16,34,46)

I ran the following code in the IntelliJ REPL and was surprised that the output was a single line, not three.

for (num in listOf(1, 2, 3)) println(num)
123

Why isn't each element on its own line?