Updating to 1.5 and having trouble with unsigned…

Kotlin: Type of the constant expression cannot be resolved. Please make sure you have the required dependencies for unsigned types in the classpath

wha?

How to do multi switch cases like Swift in Kotlin using when?

func getMode() -> Mode {
        var mode: Mode = .live
        switch (gdIsLocked, gdIsCurrent, matchIsLocked, matchIsCurrent) {
        case (0,1,0,1):
            mode = .manage
        case (1,1,1,1):
            mode = .live
        case (1,1,1,0):
            mode = .substitution
        case (1,2,1,2):
            mode = .points
        case (0,0,0,0):
            mode = .upcoming
        default:
            mode = .upcoming
        }
        return mode
    }

    enum Mode {
        case manage
        case substitution
        case live
        case points
        case upcoming
    }

Hi, is there a specific channel for asking for help about Minecraft Modding in Kotlin ? ^^

Hi All. I'm in the process of migrating a service, written in a combination of Java 8 and Kotlin, to Java 16. I am seeing some bizarre behaviour that I can't find an explanation for. The code below ends up with notTheSame set to true, when someField has the value of 2, which is the same as the value of the constant it is being compared with. (someField is read from a database). The (obviously modified) code shows the comparison:

fun isXXX(current: Foo, previous: Foo?): Boolean {
	val notTheSame = previous?.someField != someConstant
	if (notTheSame) {
		println("${previous?.someField} != $someConstant")
	}
	...
}

The data class:

data class Foo(
    ...
    var someField: Short = initial,
	...
)

The constants:

const val initial: Short = -1
const val someConstant: Short = 2

Could someone please help me understand the cause, or point me to where I should look? Code hasn't been touched for over a year, and I'm updating every single JAR used at the same time. Thanks.

This message was deleted.

Is Kotlin 1.5.21 for Intellij 2021.2(.0) going to be released?

it's seems like build in types (

Int

etc) copy on assignment, but classes create a reference on assignment. (see this simple example : https://pl.kotl.in/tTP-Co4SS). If I want to make my own numeric-ish type is there a way to behave the same as

Int

on assignment?

Not sure, but maybe with inline class ? See this modified playground : https://pl.kotl.in/U09d9eWIB

I get compiler errors about smartcasting mutable vars because it might have changed. Is there a way to disable that? It can't have changed because it's a single threaded app, and I checked for null in the previous statement, like

if( thing != null && thing.value > 10)

I can't use

thing?.value

because of a known bug in 1.5.20...

A generics question, if this is the right channel. I think I have a legitimate use of an

out

parameter, but the compiler is complaining. Error: Type parameter T is declared as 'out' but occurs in 'in' position in type (T) -> C<T>

A question about reified type parameters.

inline fun <reified T> test(): Unit {
    println(T::class.java.typeParameters.joinToString(separator = ","))
    println(T::class)
}

fun main() {
    test<Either<ReferenceObject, SchemaObject>>()
}

Is there a way I can retain

ReferenceObject

,

SchemaObject

? It looks like reified is not recursive...

How to get sum of all second element of a List<Pair<String, Int>>

I wrote my own extension function for

sumOf

on

Iterable

for my own numeric-ish type. but I'm unsure on where to put it. If I put it in the file that calls

sumeOf

it works, but if I put my impl in the file where my type is (which is where I think it should live), the compiler can't find it. Is there some magic to tell the compiler where the impl is?

Any one please explain this code. Thanks

{

    

"responseCode": 200,

    

"message": "Success",

    

"response": {

        

"Items": [

            

{

                

"purpose": "Instant Checkup",

                

"date": "16 Jul 2021",

                

"created_at": "Fri, 16 Jul 2021 09:54:10 +0000",

                

"uuid": "4aa792da-2ef8-4253-8c7c-3e3f6b9f15f3",

                

"amount": 1500,

                

"Version": "2012-10-17",

                

"Id": "4aa792da-2ef8-4253-8c7c-3e3f6b9f15f6"

            

},

            

{

                

"purpose": "Instant Checkup",

                

"date": "16 Jul 2021",

                

"created_at": "Fri, 16 Jul 2021 09:54:10 +0000",

                

"uuid": "4aa792da-2ef8-4253-8c7c-3e3f6b9f15f3",

                

"amount": 1500,

                

"Version": "2012-10-17",

                

"Id": "4aa792da-2ef8-4253-8c7c-3e3f6b9f15f9"

            

},

            

{

                

"purpose": "Instant Checkup",

                

"date": "16 Jul 2021",

                

"created_at": "Fri, 16 Jul 2021 09:54:10 +0000",

                

"uuid": "4aa792da-2ef8-4253-8c7c-3e3f6b9f15f3",

                

"amount": 1500,

                

"Version": "2012-10-17",

                

"Id": "4aa792da-2ef8-4253-8c7c-3e3f6b9f15f1"

            

},

            

{

                

"purpose": "Instant Checkup",

                

"date": "16 Jul 2021",

                

"created_at": "Fri, 16 Jul 2021 09:54:10 +0000",

                

"uuid": "4aa792da-2ef8-4253-8c7c-3e3f6b9f15f3",

                

"amount": 1500,

                

"Version": "2012-10-17",

                

"Id": "4aa792da-2ef8-4253-8c7c-3e3f6b9f15f7"

            

},

            

{

                

"purpose": "Instant Checkup",

                

"date": "16 Jul 2021",

                

"created_at": "Fri, 16 Jul 2021 09:54:10 +0000",

                

"uuid": "4aa792da-2ef8-4253-8c7c-3e3f6b9f15f3",

                

"amount": 1500,

                

"Version": "2012-10-17",

                

"Id": "4aa792da-2ef8-4253-8c7c-3e3f6b9f1511"

            

},

            

{

                

"purpose": "Instant Checkup",

                

"date": "16 Jul 2021",

                

"created_at": "Fri, 16 Jul 2021 09:54:10 +0000",

                

"uuid": "4aa792da-2ef8-4253-8c7c-3e3f6b9f15f3",

                

"amount": 1500,

                

"Version": "2012-10-17",

                

"Id": "4aa792da-2ef8-4253-8c7c-3e3f6b9f15f3"

            

},

            

{

                

"purpose": "Instant Checkup",

                

"date": "16 Jul 2021",

                

"created_at": "Fri, 16 Jul 2021 09:54:10 +0000",

                

"uuid": "4aa792da-2ef8-4253-8c7c-3e3f6b9f15f3",

                

"amount": 1500,

                

"Version": "2012-10-17",

                

"Id": "4aa792da-2ef8-4253-8c7c-3e3f6b9f1510"

            

},

            

{

                

"purpose": "Promotion",

                

"date": "16 Jul 2021",

                

"created_at": "Fri, 16 Jul 2021 09:54:10 +0000",

                

"uuid": "4aa792da-2ef8-4253-8c7c-3e3f6b9f15f3",

                

"Version": "2012-10-17",

                

"amount": 500,

                

"Id": "4aa792da-2ef8-4253-8c7c-3e3f6b9f15f5"

            

},

            

{

                

"purpose": "Instant Checkup",

                

"date": "16 Jul 2021",

                

"created_at": "Fri, 16 Jul 2021 09:54:10 +0000",

                

"uuid": "4aa792da-2ef8-4253-8c7c-3e3f6b9f15f3",

                

"amount": 1500,

                

"Version": "2012-10-17",

                

"Id": "4aa792da-2ef8-4253-8c7c-3e3f6b9f15f2"

            

},

            

{

                

"purpose": "Appointment fee",

                

"date": "16 Jul 2021",

                

"created_at": "Fri, 16 Jul 2021 09:54:10 +0000",

                

"uuid": "4aa792da-2ef8-4253-8c7c-3e3f6b9f15f3",

                

"Version": "2012-10-17",

                

"amount": 1000,

                

"Id": "4aa792da-2ef8-4253-8c7c-3e3f6b9f15f4"

            

}

        

],

        

"Count": 10,

        

"ScannedCount": 10,

        

"LastEvaluatedKey": "eyJJZCI6ICI0YWE3OTJkYS0yZWY4LTQyNTMtOGM3Yy0zZTNmNmI5ZjE1ZjQiLCAidXVpZCI6ICI0YWE3OTJkYS0yZWY4LTQyNTMtOGM3Yy0zZTNmNmI5ZjE1ZjMifQ=="

    

}

}

Can we use this kind of response For paging library 3 ?

@haris mehmood please, minimize long snippets, many of us are on mobile, walls of text like yours make checking the channel harder .

This message was deleted.

I have a

List<String>

with about 250 URLs. Currently I am doing a

GET

request to each url in a forEach loop so it’s synchronous. Obviously one of Kotlin’s amazing features is co-routines. Does anyone know of a good resource on how I could do this async? It’s currently taking 30 seconds while I feel like this could be done much much quicker async. Note I own all 250 URLs that are getting visited so I am not spamming anyone

When is it appropriate to use the

!!

operator? Example: In an edit and delete situation I never expect the

todoId

to be null, only when a new todo was added. Does it make sense to just use

!!

then instead of the null-safe operator?

fun onAddEditResult(result: Int, todoId: Long? = null) {
        viewModelScope.launch {
            when (result) {
                RESULT_TODO_ADDED -> eventChannel.send(Event.ShowTodoSavedConfirmationMessage("Todo added"))
                RESULT_TODO_EDITED -> {
                    eventChannel.send(Event.ShowTodoSavedConfirmationMessage("Todo updated"))
                    setExpandedState(todoId!!, false)
                }
                RESULT_TODO_DELETED -> {
                    val todo = todoDao.getTodoById(todoId!!)
                    todo?.let {
                        todoDao.delete(todo)
                        setExpandedState(todo.id, false)
                        eventChannel.send(Event.ShowUndoDeleteTodoMessage(todo))
                    }
                }
            }
        }
    }

How do you override the equals operator so that you can apply it to sibling classes? I always get Operator '==' cannot be applied to 'Length.Kilometer' and 'Length.Meter' in the below example. Kotlin Playground: https://pl.kotl.in/uT4Ch5mem

abstract class Length {
    abstract val meters: Double

    override fun equals(other: Any?): Boolean {
        if (this === other) return true
        if (other !is Length) return false
        return meters.equals(other.meters)
    }

    override fun hashCode() = meters.hashCode()

    class Meter(value: Double) : Length() {
        override val meters: Double = value
    }

    class Kilometer(value: Double) : Length() {
        override val meters: Double = value * 1000.0
    }
}

fun main() {
    val oneKm = Length.Kilometer(1.0)
    val oneThousandMeters = Length.Meter(1000.0)

    println(oneKm.equals(oneThousandMeters))
    // true

    println(oneKm as Length == oneThousandMeters as Length)
    // true

    println(oneKm == oneThousandMeters)
    // this will not compile: Operator '==' cannot be applied to 'Length.Kilometer' and 'Length.Meter'
}

Hi, why can't I use a vararg argument for a typealias of a function ?

Sealed class Item( val name: String) { object Item1: Item("Mango") object Item2: Item("Grapes") } How to add Item objects in a list with function? Sample: val items = listOf( Item.Item1, Item.Item2)

Hi, I am building a web app using kotlin. The team suggested using kotlin backend and angular front end but I’m not sure if kotlin integrates well with angular. Is that true? Also, if there is ktor to create a full stack kotlin web, why not use that? I’ve read a lot of pros of Kotlin in full stack but can’t seem to find any cons. Are there any? Thanks.

Hi, When I write code like this on a setter function, I am getting the following error Type mismatch. "*Required: Unit, Found: Boolean*".

var isRectangle: Boolean
        get() = field
        set(value) = value.not()  // The error is here

How is it possible to return a Unit type when we use a syntax like "set(value) = " . Thanks in Adavance

(I mean how can it (the singleton

AmountScreen

) be null?)

hi is there better way to frame this code

fun make(rows: Int, cols: Int): String {
    val table = StringBuilder()
    for (rpos in 0..rows) {
        table.append(START_ROW)
        for (cpos in 0..cols) {
            val cell = "${START_CELL}${cpos+rpos}${END_CELL}"
            table.append(cell)
        }
        table.append(END_ROW)
    }
    return table.toString()
}

When developing gradle plugin in Kotlin, IntelliJ gives me such errors:

Cannot access class '<http://java.io|java.io>.File'. Check your module classpath for missing or conflicting dependencies

or

Cannot access class 'java.util.concurrent.Callable'. Check your module classpath for missing or conflicting dependencies

But there are no errors when building this project from Gradle command. Any ideas what can be wrong?

How to auto apply init block after applying a functional block ? Take this code for example :

class Config(var degree: Double = 315.0) {
  init {
    require(degree > 180 && degree < 360)
    { "degree should between 180 and 360" }
  }
}

And if we initialize

Config

directly , it will check the value as expected :

@Test
fun normalTest() {
  try {
    Config(90.0)
    fail()
  } catch (e: Exception) {
    assertTrue(true)
  }
}

But if there is a function accepting the

Config

as functional object :

private fun calculate(block: Config.() -> Unit = {}) {
  val cfg = Config().apply(block)
  println("do something... with degree = ${cfg.degree}")
}

@Test
fun testCalculate() {
  try {
    calculate {
      degree = 90.0
    }
    fail("It SHOULD fail")
  } catch (e: Exception) {
    assertTrue(true)
  }
}

It will skip the

init

check block . How to solve this problem ? Thanks. I could only think of this solution :

class Config(var degree: Double = 315.0) {
  init {
    check()
  }

  fun check() {
    require(degree > 180 && degree < 360)
    { "degree should between 180 and 360" }
  }
}

and …

private fun calculate(block: Config.() -> Unit = {}) {
  val cfg = Config().apply(block).also { it.check() }
  println("do something... with degree = ${cfg.degree}")
}

But I think it is so ugly … Is there any better way ? Thanks.

Hi I have been trying to use the MANIFEST.MF file to hold on to some basic metadata info such as the build version... following some Stack Overflow responses which use methods like

MyApplication::class.java.`package`.implementationVersion

or

Thread.currentThread().contextClassLoader.getResources(JarFile.MANIFEST_NAME)

but they all result in a NULL. I looked deeper, IntelliJ doesn't even create a MANIFEST.MF when Running/Debugging (although it does when `gradle build`'ing a JAR file). Any tips on what I'm doing wrong? (this is NOT an Android project)

Hello mates, why there is such a restriction on named params? I mean, ofcourse Java cannot have named params, but I'm used to put param names for kinda not obvious consts, so I can view the file without IDE and see what this values mean. It may be useful if I could 'name' the param but keep its position, so after compilation param names will be just erased. UPD: Preventing misunderstand: • compiler should check that the order and names are correct • in runtime actually arg names should be erased