How to varargs to a map inside a custom Exception Hi all, I need to pass the following varargs to a map. How can I do that? I come from the java background. open class DomainException(msg: String, vararg val msgParams: String) : Exception(msg) 1 post - 1 participant Read full topic

Code style: absent-value in enums I have an enum class like the following enum class ErrorCause(val id: Short) { Electrical(1), Mechanical(2), Chemical(3); } However, the class that includes a field of type ErrorCause must not necessarily contain an error cause, so the value is effectively optional. class Thing { var errorCause: ErrorCause? = null // to null or not to null, that is the question! } Would you prefer to add an enum value to express absence of an error cause like in this example: enum class...

Polymorphic serialization doesn't work for deeper sealed class hierarchies I have the following code: @Serializable sealed class Component : Tagged { @Serializable @SerialName("name") data class Name(val name: String, @Transient override val tag: Tag = Tag.Name) : Component() @Serializable @SerialName("parent") data class Parent(val parent: UUID, @Transient override val tag: Tag = Tag.Parent) : Component() @Serializable @SerialName("entity_type") sealed class EntityType : Component() { @Transient override val tag = Tag.EntityType...

Serialization works, deserialization doesn't I have the following code (sorry for the dump): @Test fun timestamp() { val timestampGenerator = DistributedTimestampGenerator(32) val timestamps = listOf( timestampGenerator.generate(), timestampGenerator.generate(), timestampGenerator.generate(), ) val serialized = serializer.encodeToString(timestamps) val deserialized = serializer.decodeFromString(serialized) assertEquals(timestamps, deserialized)...

Should i use nullable or default values in data classes? Hi, I have an endpoint that receives a data class object, some properties can be not sent, but it is required and I will validate before enter in my system. After my data is valid, i will convert to entity and do some stuffs, so my classes will be like this: data class CreateCategoryRequest( @field:NotEmpty val name: String?, @field:Positive val price: BigDecimal? ) class CategoryEntity( var name: String, var price: BigDecimal, ) When I try to convert request to entity I...

View source of Kotlin package in Eclipse Dear guru, I am using package written in Kotlin (OkHttp) in my Java project in Eclipse. This package has sources jar attached. When I want to look at the sources (following up some method link, etc) I expect that Eclipse will show me that source as Kotlin one (I have Kotlin plugin installed) but I see it as a Java source without ability even to navigate to methods in Outline view … Is it possible to solve that problem somehow? Thanks in advance, Vadim 1 post - 1 participant...

KDoc module level 2 headings don't seem to be working Hello, I’m trying to follow the Kotlin KDoc module formatting guidelines and I’m seeing everything squished together in my javadoc. Am I doing something wrong or is this a known bug? # Package com.my_package Classes More text ## Level 2 heading ## Testing... And this is what shows up in the generated javadoc: ClassesMore textTesting... Thanks, Daryl...

Make "real" apps straight in the browser HTML, CSS and JavaScript suck. Compare Google Spreadsheets (the web version) with OO Calc. It’s a huuuge difference. Not sure exactly what makes the difference, but using the web versions feel kind of annoying. HTML, CSS and JavaScript were probably not created for developing “apps”, but for showing simple content on typical “web sites”, present information. I’m very new to WASM. Will WA make it possible to develop apps straight in the browser that look and feel exactly like a desktop app?...

onDestroy function completion I need my app to call and finish a runnable routine the moment my application is being destroyed. I’ve done some code and it seems to partially work. My goal is to send a small command (consisting of only one character) through a socket opened in a network connection so as to let the server know that the application is closing. The code seems to be working. I can see the reports of the Log instructions in the debugger window, although in the wrong order: D/Debug:: On Destroy entered…...

Infix function returning String Hi, I’ve got simple class: class Person(val name : String, val age : Int) and infix function: infix fun Person.to(other : Person) = “name {other.name}” For the following data: println(Person("name",16) to Person ("last name", 0)) I want output like: name lastname But instead I’ve: (com.other.Person@2d6e8792, com.other.Person@2812cbfa) Why I’m getting result like that? 1 post - 1 participant <a...

Is JVM reflection broken? I noticed an inconsistent behavior in reflection methods when trying to access some static properties of types in java.lang via reflection. I’ll provide further details below. The main question here is: am I missing something or is there some bug in the reflection library? Details On Kotlin JVM Kotlin, some basic types (e.g. Long, Int, etc) come with a companion object letting developers access static properties and methods of the corresponding JVM types. Accordingly, Kotlin reflection lets...

I'm confused by the protected modifier Could you explain me why the line it.protectedProperty = 0 in the CompositeImpl class doesn’t work? // Kotlin 1.4.21 sealed class Component { var protectedProperty: Int = 0 protected set abstract class Leaf : Component() abstract class Composite : Component() { abstract val children: List } } class CompositeImpl : Component.Composite() { private val _children = arrayListOf() override val children: List by ::_children fun a() { // This...

How to get back to login screen once user click on signup button in kotlin? I am beginner so if anyone help me i will be grateful thanks in advance 1 post - 1 participant Read full topic

Kotlin react table example Hi, does anyone know how to use kotlin react table wrapper? (kotlin-wrappers/kotlin-react-table at master · JetBrains/kotlin-wrappers · GitHub) There’s no example in the repo or test classes that show the usage. I’m not very familiar with react, just started learning. Thanks. 1 post - 1 participant <a...

How to add Java classes support into multiplatform project (Android/JVM/JS) Hi all, I am creating multiplatform library which has three targets Android, JVM and JS. My library has common Kotlin code and platform specific code. Currently most platform specific code for JVM and Android is done on Java and I do not have time to migrate it to Kotlin now. How to add support of Java classes for jvmMain and androidMain source sets? When I add withJava() option into build.gradle it writes me an error that Java plugin is not compatible with Android plugin. And this is true,...

Reverse C interop passing array to Kotlin Native and back Hello, I got stuck while trying to write a library where kotlin code is called from another C library which is loaded in another application with a strict interface so I was following these tutorials to see how the interop works: https://kotlinlang.org/docs/tutorials/native/dynamic-libraries.html#using-generated-headers-from-c But unfortunately, there is...

Spotify-web-api-kotlin - Kotlin multiplatform Spotify API wrapper (JS, JVM, Native) Hi, spotify-web-api-kotlin, a Kotlin MPP Spotify API wrapper that I’ve been working on for the past few years has become mature enough that I thought I’d share with all of you, and is available at https://github.com/adamint/spotify-web-api-kotlin. The library targets Kotlin/JS, JVM, and Native desktop OSes (Windows/Linux/macOS) and will soon also add iOS as a target. It’s the only Kotlin MPP and...

Why is Kotlin's cast more weakly typed than Java's? With Java the following fails to compile: String s = "abc"; Integer i = (Integer) s; // fails to compile - "Inconvertable types" error But Kotlin’s cast does not cause a compile error when used in this way: val s: String = "abc" val i: Int = s as Int // compiler is happy with this but guaranteed to fail at runtime Java’s casting mechanism seems superior - more errors are caught at runtime. I’m curious why Kotlin weakened the type of the “as” operator here? 1...

Java dependent Kotlin, run for iOS I was having a Java code for android application. I want to use same code for iOS also, after reading the flexibility about Kotlin multiplatform, thought to give a try with new cross platform solution. I converted the Java code to Kotlin, and copied in shared component in the KMP project. it ran perfectly for Android. But ran with multiple error of iOS, As the shared code have JAVA util,time,net and security packages dependency. So this code didn’t work for iOS. My question is can we run...

View binding vs android extension Hi guys, I want to know if view binding is mandatory because all the lessons I’m on at Udemy use android extensions. When asked, they say keep to synthetics/extensions. There was one course using view binding but when I do recycler view, especially in the onBind method it throws ‘unresolved reference’ errors even after declaring variables in main activity. and the instructor has gone unresponsive. Pls clarify, thanks a lot! 1 post - 1 participant <a...

Dokka - generate documentation for specific files Hi. Is there a way to configure Dokka to generate documentation for specific files instead of specific packages? I couldn’t find a way from the documentation. Is there something I’m missing? Thanks 1 post - 1 participant Read full topic

Error implementing multiplatform library dependency in Android project Hello, community! I have created Kotlin Multiplatform library “c4view-worldwind” with Android, JVM and JS targets. I have successfully publish this library into maven local repository. I can see all classes, resources, manifest and meta info inside local repository “~/.m2/…” folder. I have successfully added dependency to my library in my Android application using following code: implementation ('vision.combatc4view worldwind android1.0-SNAPSHOT@aar') {transitive=true} But when I try to...

Make reactive declarations part of the language One of the big pains of programming is to keep track of what happens in what order. When you get a back, you need to step into the code and investigate what happened in a certain case. With reactive programming this problem is eliminated. An example is a spreadsheet. A1 = B2 * 2, means that A1 always will be equal to B2 * 2. When B2 changes, A1 changes too. We have got many nice web frameworks, like React, Vue and Svelte, that also work this way: Here is an example of reactive declarations in...

Kotlin compilation StackOverflow Failure Hi all, We are using Kotlin + Spring to develop a web application. Recently, we observed the compilation is not stable and sometimes the build failed with StackOverflow exception. The kotlin version is 1.4.21-2 (the latest one) and we are using maven to build. The followings are the error messages. [ERROR] java.lang.StackOverflowError at org.jetbrains.kotlin.cfg.ControlFlowProcessor$CFPVisitor.mark(ControlFlowProcessor.kt:174) at...

Anyone has tried next.js with kotlin/js? I am wondering if using next.js from Kotlin/JS would be a good option… Any opinions? experiences? 1 post - 1 participant Read full topic

Using CompletableJob to wait for send operation running in the background I have code that runs a send loop in a background coroutine. I transmit send requests through a Channel to that loop, and use an associated CompletableJob to be able to wait until that loop actually sent the data. Pseudo code: data class SendOperation(val data: ByteArray, val job: CompletableJob = Job()) val sendChannel = Channel(Channel.UNLIMITED) // Called internally by another function private suspend fun runSendLoop() { while (true) { val operation = sendChannel.receive()...

Remember Me Hello guys I am trying to make remember me button in kotlin but I cant run app because of this 1 post - 1 participant Read full topic

Multiple edittexts to txt file and send via email Hi there, I have like 440 edittexts of numbers in my layout and I want to save them into the text file (. txt) and then this file send via email. Can anyone help me with the code to make this happen? I’m rookie with kotlin,and I’m guessing that the best ways are arrays or for loops. Many thanks to all 1 post - 1 participant Read full topic

Multiple invariant parameters leads to type compilation failure? interface Animal class Cat: Animal class Dog: Animal data class BoundedInvariant(val thing: T) data class SecondBoundedInvariant(val thing: T) fun pet(invariant: BoundedInvariant) { println(invariant.thing::class) } fun petBoth(secondBoundedInvariant: SecondBoundedInvariant, invariant: BoundedInvariant) { println(invariant.thing::class) println(secondBoundedInvariant.thing::class) } val animalSet = mapOf( BoundedInvariant(Dog()) to SecondBoundedInvariant(Dog()),...

Using a KClass reference as a reified parameter to deserialize from JSON I’m trying to implement a general serialization framework to convert outgoing and incoming messages to json using the kotlinx serialialization. I’m developing a multiplatform app, so I’m trying to get it to run on KotlinJVM and KotlinJS. For this, I add a type field to every message and use a map that maps each type string to a KClass. What’s the type for that map? It contains KClass objects whose classes extend the Message class, therefore in java I’d specify my map as Map(json) }...