How to handle serialization with a class hierarchy What is your use-case and why do you need this feature? I need to serialize some classes like the following. interface WalletRequest @Serializable data class Create(val user: String, val amount: Double) : WalletRequest @Serializable data class Transfer(val from: String, val to: String, val amount: Double) : WalletRequest @Serializable data class Amount(val user: String) : WalletRequest val walletRequestModule = SerializersModule { polymorphic(WalletRequest::class) {...

Block an asynchronous call from a foreign API Hello everyone! I’m currently developing an HTTP server with Ktor backed by the BFT-SMaRt library. The BFT-SMaRt library is a Byzantine Fault Tolerant State Machine Replication library, our usage is to replicate system operations across nodes. This library has an async call <a...

How to do nullable generic List correctly? Hi I am trying to write a generic function taking an optional list of types as argument like the following: // Kotlin fun callWithRetry(onError: List?, onAnother: List?) { onError?.forEach { println(it) } onAnother?.forEach { println(it) } } However, whenever I am trying to call this function with both null parameters, it would complain Not enough information to infer type variable T to me. callWithRetry(onError = null, onAnother = null) // `Not...

Cyrillic input not recognized in Kotlin Native You may find attached a screenshot with the simplest Gradle - Kotlin|Native project. You may easily notice that the English input is being recognized perfectly, while the Cyrillic input gives the blank result. This happens in IDE terminal window and in separate CMD as well. Can anyone explain what’s wrong with Kotlin interpretation of foreign codepages? Thank you. PS. The same code compiled for JVM works fine under the condition that codepage in CMD is changed to 1251. <a class="lightbox"...

kotlin-multiplatform : how to use Kotlin Flow in Javascript I have created a kotlin multi-platform library to design Domain layer that targets JVM and JS (nodejs and browser). Domain depends on UseCase, UseCase depends on Repository, Repository depends on Service and Database. AFAIK, Kotlin Coroutines work across platforms (JS/JVM/Native). I have a function that returns Flow , instead of Promise . fun getUserList() : Flow{...} Reason is, I want to update UI as soon as there is any change in Database. On JVM (or Android), I know how to consume Flow....

Why toDouble() or even toInt() functions not available in android studio (kotlin)? Do I have to import a specific file to make them available? Why toDouble() or even toInt() functions not available in android studio (kotlin)? Do I have to import a specific file to make them available? 1 post - 1 participant Read full topic

GUI for Kotlin|Native Dear All, I assume that there is a shortage of GUI tools for Kotlin|Native. I’ve been advised that currently the only alternative is libui (https://github.com/msink/kotlin-libui). When I tried to use it, I noticed that it has virtually no documentation apart from autogenerated. For me as a newbie to both Kotlin|Native and GUI it’s virtually impossible to use it. My two requests: Can anybody help me providing fully...

How to iterate list which has been unsafeCast-ed from JSON Hello, I am struggling with simple for loop of list common data objects generated from JSON in Javascript. The error I get is: TypeError: “availableBooks.iterator is not a function” The list is generated this way: fun main() { MainScope().launch { val availableBooks = getAvailableBooks() val innerHtml = StringBuilder().append("Aplikacia je nacitana: ") console.log(availableBooks) println("${availableBooks::class}") for (availableBook in...

Contracts, lambdas and captured vals I’ve been playing with contracts and wanted to confirm the behaviour I’m seeing. Suppose I have the function block defined below - I’m calling the lambda directly, but we should imagine that this will be called outside of this execution (but still exactly once), hence we aren’t making the function inline as lambda would need to be noinline anyway. @UseExperimental(ExperimentalContracts::class) fun block(lambda: () -> Unit) { contract { callsInPlace(lambda,...

Interop library AtomicFU can't be exported with -Xexport-library I am trying to compile project with atomicfu dependency without luck. Changing version of Kotlin and atomicfu itself does not help. Here is a log. Any ideas? w: Interop library /Users/dmitrykolesnikovich/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlinx/atomicfu-iosarm64/0.14.1/f01f78fe2f58e131726e47a7f8ef20f94d8dc9f3/atomicfu-cinterop-interop can't be exported with -Xexport-library e: Compilation failed: Could not find serialized descriptor for index: -6614713790654178244...

How to call joinToString with suspending function This is a toy example of what i want to accomplish: import kotlinx.coroutines.delay suspend fun x() { val names = listOf("Abe", "David", "Boris") names.map { toUpper() }.joinToString() } suspend fun toUpper(name: String): String { delay(100) return name.toUpperCase() } names.map { toUpper() }.joinToString() is not nice and android studio says that it can be simplified to names.joinToString { toUpper() } Unfortunately this does not work because now there is an error:...

Pretty Much the entire Android User uses libraries that square created Like okhttp, picasso, retrofit, leakcannary, dagger How Android World would look different without square? 1 post - 1 participant Read full topic

Observe mutuableMapof in android Hi, Is it possible to observe a map list? This is my map: var map = mutableMapOf() I would like to notify to UI when the list gets any changes, is it possible? My goal is to observe a map, so if there are others way to reach my objective, please let me know. Thanks 1 post - 1 participant Read full topic

Understanding data classes in kotlin This is my class class Foo(private val b: B) { override fun equals... override fun hashCode... } If I do assertEquals(foo1, foo2) where foo1 and foo2 are of type Foo and if foo1 and foo2 are not equal, I get the error message like Actual: Foo@f54e1c3c Expected: Foo@ee2bcc2d But if I change Foo to a data class (i.e just add the keyword data before class Foo) and execute the assert statement, then I get a detailed error message with the full values of foo1 and foo2 instead of the hashcode...

Mockk package level lazy property Forgive me if this is not the right channel. I am trying to mock some lazy package level property using Mockk. package com.aaa.bbb internal val isEnabled by lazy { Config.find("enabled") // boolean } // use isEnabled fun featureName() { return if (isEnabled) { "feature-name" } else { "nothing" } } Then in my test i have the following: // This would pass @Test fun `test enabled case`() { mockkStatic(Config::class) every { Config.find("enabled") } returns...

Kotlin Spring boot issue Hi friends I’m new to kotlin, I just develop simple kotlin application with spring boot. Development process was done. Now I’m trying to deploy the application so I get deployment file (Jar/War) by using gradle bootWar command , I successfully get that file but I’m not able run that file using java -jar application.jar I’m getting some error I don’t know what is the error.? Error details and code available in this below stackoverflow Link please help me to fix this issue. Thanks in advance <a...

Internal function parameter name I’ve been getting into Swift recently and noticed that it is incredibly similar to Kotlin. Something that Swift has and I think would be of great help for the Kotlin community to improve code legibility even more is the addition of internal function parameter names (referred as ‘argument labels’ in Swift’s documentation) to Kotlin. So, for example, if we have a function to greet someone, we’d...

How to use ktor auto reload (live refresh) that using gradle kotlin dsl? I want to develop server and client web with ktor, but when coding I don’t want to restart application every time. How could I do with this option? This main application: fun main(args: Array): Unit = io.ktor.server.netty.EngineMain.main(args) Kotlin version: 1.3.70 Ktor version: 1.3.2 1 post - 1 participant Read full topic

Why do we override a function Hi i am new in kotlin. I am a new learner of kitlin (android studio). I would like to know why do we override a function. I have been overriding some functions that return “Run” so they can return “Walk” but i don’t really know the importance I could just write “Walk” 1 post - 1 participant Read full topic

(Beginner) Why does this example code print kotlin.unit? Hi all, I am working through Kotlin in action and have the following code enum class Color ( val r: Int, val g:Int, val b:Int ) { RED(255,0,0), ORANGE(255,165,0), YELLOW(255,255,0), GREEN(0,255,0), BLUE(0,0,255), INDIGO(75,0,130), VIOLET(238,130,238); fun rgb() = (r * 256 + g) * 256 + b; } fun getMnemonic(color:Color) { when (color) { Color.RED -> "Richard" Color.ORANGE -> "Of" Color.YELLOW -> "York" Color.GREEN -> "Gave"...

Kotlin and megamorphic interfaces This is a question for general knowledge. I stumbled over this interesting issue in Guava: <a>https://github.com/google/guava/issues/1268</a> There a smart person complains that the performance of google ImmutableList is much worse then ArrayList. This was due to the fact that there were 3 types of ImmutableList. Empty, Singleton and Regular. Therefore the call sites were converted into megamorphic call sites. They dropped the EmptyImmutableList and then the call sites were converted into...

Time out while accessing huge list/collection what is the best way to traverse huge list/collection in kotlin? is there any fast way available which reduce the time of traversing the list? I have tried parallel stream but it did not work … 1 post - 1 participant Read full topic

Use renderscript (openMP like) for Collection Operation I this will be great support OpenMP like operation for perfomance UP becouse GPU is not used in may applicaion and its more “threads” fot corrrutines. 1 post - 1 participant Read full topic

Define default corrutine for filter operation If i have function wuth mant DB or Net usage + many list manupulation i muse defne must operation. 2/ If i use corrutines in Main thread and want to filter big collection i can use “collection.fillter.map.forEach {UITHreadFunc Or not i do’t want reseach each ttime}”. In main thread its slow down, in default i can get exceptuion. Why we dont use Executors.Default for all collection operaion (except function body execution) if for context now is Default.Main? It’s will be great smart feature 1...

Auto mark all IO function to suspend I think we can mark all system IO fuction (fle, socket) (or if it rise IOException) and mark its for “must have suspend in kotlin” 1 post - 1 participant Read full topic

Exception during code generation Im trying access the data class in Java and in order to use I have applied @JvmOverloads constructor. Is there any limit for number of fields in the data class, when using @JvmOverloads ? It’s failing at run time. java.lang.IllegalStateException: Backend Internal error: Exception during code generation. 1 post - 1 participant Read full topic

Gradle multiplatform build fails Trying to run gradle publishToMavenLocal on a kotlin multi platform project and i get the following error An exception occurred applying plugin request [id: 'org.jetbrains.kotlin.multiplatform', version: '1.3.72']

Failed to apply plugin [id 'org.jetbrains.kotlin.multiplatform']

> Could not create plugin of type 'KotlinMultiplatformPluginWrapper'. > org/gradle/api/internal/FeaturePreviews Any body know why? 1 post - 1 participant <a...

Need help I try to add a spinner with a listview in the same activity forwich when I click on item (country) listview show (cities ) but don’t work 1 post - 1 participant Read full topic

Compiler Error I try native kotlin but When i compile this is returned : Compilation failed: The /home/etienne/.konan/dependencies/clang-llvm-8.0.0-linux-x86-64/bin/clang++ command returned non-zero exit code: 127 1 post - 1 participant Read full topic

Packing/Exporting dependencies via Gradle Hi everyone, I have some proto files in my Project A and am using the protobuf plugin to generate the java files. In another gradle file, I’m creating a JAR so I can upload it to the cloud and download in the Project B. The problem I’m having is with the dependencies since packing them along with the java files in this JAR, would not be ideal because of the file size(~10MB). So, what would be the best way to have these dependencies in the Project B and in any other project that needs to...