It seems every reference in Kotlin either extends Any, or implements kotlin.Function. if there is a generic field is there any way to get the type of the function so it can be executed? Appears type data is erased and impossible to do anything like

is () -> Unit

I need to throw an exception using reflection, any examples? The exception type is a string

Is it possible to do something like this? I want to avoid switching on each potential type. Does type erasure make it impossible?

data class DataDriver<T>(val valueCalculator: (T) -> Int)

val dataDriver = listOf(
        DataDriver<T1>( ::calcValue1),
        DataDriver<T2>( ::calcValue2)
)

// Using reified worked here
private inline fun <reified T> query(isSubmitted: Boolean): List<T> { 
	return realm.where<T>().equalTo("submitted", isSubmitted).find()
}

fun calcValue1(item: T1) -> Int {
	return 42
}

// But what about here?
// Apply transforms to get a list of calculated items,
// calling the proper query and calculator based on the type.
// Without resorting to type checks for each type.
// IS THIS POSSIBLE?
dataDriver.map {
	query()  // type inference fails here
		.map(::valueCalculator) 
}

Do data classes need unit tests if we know they only have a primary constructor and no methods? data class(val id: String, val firstName: String, val lastName: String)

Currently, when refactoring a package that has the common name ommited, the refactor changes the package name to not include the common name, and this doesn't seem right. No compiler warning, #detekt doesn't get it, and IntelliJ doesn't do it's job correctly

Why doesn't Kotlin contain default value for type parameters?

class Foo<T = Any>(val t: T = Any())
...
Foo()

if I type

override fun equals(other: Any?): Boolean = when(other) {
        this -> true

will

other

checked using == or === ?

Hi there, have a QQ, let me know if this is not the right channel. By calling <string>.startsWith("$$"), I see some IllegalArgumentException reports coming from that: Caused by: java.lang.IllegalArgumentException: at kotlin.text.StringsKt__StringsJVMKt.b (StringsKt__StringsJVMKt.java) at kotlin.text.StringsKt__StringsJVMKt.startsWith$default (StringsKt__StringsJVMKt.java:195) I checked the code and dont see anything related and why this might be throwing such exception. Unfortunately I dont have a sample string that is causing the issue.

Is there a way to iterate over a List of reified types?

https://twitter.com/kotlin/status/1131923611185504258 Any plans for the weekend? #KotlinHeroes (https://www.jetbrains.com/promo/kotlin-heroes/) practice round is running and open for everyone: https://t.co/ba3axjdx6C. Test your skills or have fun solving problems in #kotlin! Twitter

i am looking for a commandline parsing library that supports sub commands and is not hardcoded to println() everything idally i want to pass a custom logger to it, but the frameworks i looked at so far did not have the capability for that also subcommands and not killing the app on failure would be nice (looking at clickt) does anyone know which commandline parsers might cover at least some of those features ?

I’m trying to use kotlin

1.3.40-eap-32

but my build is failing with something like:

Could not resolve org.jetbrains.kotlin:kotlin-test-common:1.3.40-eap-32.
         > Could not get resource '<https://dl.bintray.com/kotlin/kotlin-eap/org/jetbrains/kotlin/kotlin-test-common/1.3.40-eap-32/kotlin-test-common-1.3.40-eap-32.module>'.
            > Could not GET '<https://dl.bintray.com/kotlin/kotlin-eap/org/jetbrains/kotlin/kotlin-test-common/1.3.40-eap-32/kotlin-test-common-1.3.40-eap-32.module>'.
               > <http://dl.bintray.com|dl.bintray.com>

Is this the expected behavior for now? Until it is not released?

Hi guys! Can you please help me properly setup maven pom.xml to execute JUnit 5 Jupiter tests in mixed Java + Kotlin project. Can someone of you provide me worked example? PS: I have also posted similar questions on JUnit GitHub and StackOverflow: - https://github.com/junit-team/junit5/issues/1899 - https://stackoverflow.com/questions/56306835/pom-xml-maven-configuration-to-run-junit-4-junit-5-jupiter-tests-in-mixed-java?noredirect=1#comment99224282_56306835 Thanks! --- Regards, Maksim

Does anyone knows if it’s possible somehow configure maven pom.xml to allow java tests to be recognized from

src/test/kotlin

folder? I prepared an example you can quickly clone and verify:

git clone <https://github.com/daggerok/mixed-kotlin-java-jupiter-tests> testme ; cd $_ ; mvn test

here kotlin tests could be recognized from both

stc/test/kotlin

as well as from

src/test/java

, but java test classes are visible only from

src/test/java

Let me know if you know how to tell maven in it’s pom.xml project build configuration also recognize java tests classes from

src/test/kotlin

directory too Thanks

Is not being able to call extension class methods from another class (https://youtrack.jetbrains.com/issue/KT-24290) design choice or shortcoming of the compiler? It makes class methods that extend

CoroutineScope

(needed by convention) quite awkward to call.

hi! What kind of compiler architecture does Kotlin have?

@SqlMarker
object SQLBuilder {
    fun query(init: SqlSelectBuilder.() -> Unit): SqlSelectBuilder {
        val builder = SqlSelectBuilder()
        builder.init()
        return builder
    }
}

I have this, but somehow the compiler still let me do this eventough I marked it with DSLMarker

val query = SQLBuilder.query {
        
        query { 
            
        }

what am I doing wrong? 😞

Is an enum or a sealed class better for a large number of entries (i.e. emojis) ? I tried a sealed class but the IDE marks them as unused (they're part of the API) and it's very laggy

Hi, is there a rxkotlin related channel?

Hi all, I have a question about kotlin (v1.3.31) reflection.

fun main(args: Array<String>) {
    fun <P1, P2, R> ((P1, P2) -> R).partial(p1: P1): (P2) -> R = { p2: P2 -> this(p1, p2) }

    fun regexMatch(re: Regex, s: String): Boolean = re.containsMatchIn(s)
    val match = ::regexMatch.partial(Regex("^123"))

    println(match("12345"))
    println(match("123xx"))
    println(match("2345"))
    println(match)
    println(match.reflect()!!.run {
        "(${parameters.map { it.type }.joinToString()}) -> $returnType" })
}

The output (the signature of

match

) is

(P2) -> R

. Is there any way to infer the actual correct signature which should be

(String) -> Boolean

?

is there a generic constraint to enforce equals operator?

Hi, I noticed a common problem when modeling using Sealed classes and Data classes. In my projects, this approach is too common and we noticed a boilerplate problem when we need to modify the content using the copy method of data classes. Currently, Kotlin does not provide a way to restrict the Sealed classes implementations to Data classes, so if you want to use copy method, you need to check for all concrete data classes and it is a pain in the ass. Imagine the next scenario:

sealed class MyModel {
        abstract val name: String
        abstract val title: String
}
data class Model1(
            override val name: String,
            override val title: String,
) : MyModel()
...
data class Model100(
            override val name: String,
            override val title: String,
) : MyModel()

If you want to modify the title, for example, adding the environment where you are running your code could be similar to:

fun MyModel.addEnvironmentToTitle(env: String) = when (this) {
	is MyModel1 -> copy(title = title + env)
	... -> // Same boilerplate here
       is MyModel100 -> copy(title = title + env)
}

It is a simple example but you could have more complex code and it becomes unmanageable. Does anyone know if we will have in the future an option to restrict Sealed classes implementation to Data classes? With that restriction previous method would be:

fun MyModel.addEnvironmentToTitle(env: String) = copy(title = title + env)

anyone here using inline class with mockito before? Mockito gets confused when I’m trying to mock a method with the return type is an inline class. It basically says something like

can not mock this method with return type String but got Url instead

Hey, do we have a map function but where I can “skip” returning elements depending on some condition? Kind of a reduce?

will anyone register to the kotlin hero contest ? i'm trying to enter using gmail into the codeforces.com, but I'm unable to login into the site, anyone with problems?

Does nobody know more about this general problem??

It kinda seems like this exception that is happening is just being silently snuffed out

is there any built-in annotation to suppress 'unused' warnings for methods in a library? i.e. 'API methods' used by other code. or a good way i could define one?

I could really use unsigned types (parsing a binary format)… how sane is it to adopt unsigned types at their current maturity? Are they experimental like coroutines (works great, but api changes may come) or experimental like running a prerelease jvm (all hell may break loose, etc)?

Admin please create a separate channel for Kotlin-Multiplatform