Just published an article about value-based classes and using Kotlin's type system to enforce your domain rules. https://medium.com/@dev.ahmedmourad73744/value-based-classes-and-error-handling-in-kotlin-3f14727c0565?source=friends_link&sk=a16186408e1c8e317e3e11fd16e33710

I'm looking at a way to be able to produce an anonymous object that implements multiple interfaces, but seemingly missing something with the below resulting in a

Type mismatch. Required: P, Found: <P>

error for the returned value.

interface A
interface B
interface C

fun <P> resolve(): P where P : A, P : B, P : C {
    return object : A, B, C {}
}

Is there some variation of this that is possible?

Often when I try to handle generics I run into this casting situation, which generates a warning that I don't understand:

abstract class TodayDynamicModel<V : View> : BardeenListUiModel() {

    fun asTodayDynamicModel() = this as TodayDynamicModel<View> // --> Unchecked cast: TodayDynamicModel<V> to TodayDynamicModel<View>
}

Isn't

V

guaranteed to be of type

View

?

https://github.com/jetbrains/kotlin/releases/tag/v1.4.10 has just been released, but the release name on GitHub is incorrect: it says 'v1.4.0' I already notified @stanislav.erokhin about this (he made the release), but I'm not sure if he reads messages on this Slack environment. @JB

Congratulations on :kotlin: 1.4.10 release, new inference is on point! 👌

Help needed - I get an exception: org.jetbrains.kotlin.codegen.CompilationException: Back-end (JVM) Internal error: wrong bytecode generated Boiled it down to that piece of code:

fun s() = sequence<Unit> {
    suspend fun f() {
        let { f() }
    }
}

Anyone an idea how I need to replace/annotate

let

to get that up and running? (bug is in 1.4.0 and 1.4.10) - Thanks in advance!!!

So really 1.4.10 is a patch release - libraries compiled by 1.4.0 are comatible with 1.4.10, and vice versa.

Hello, It looks like Kotlin 1.4 is bringing new stuff! Any reason why this breaking change? Code

fun <T: Any> x(block: () -> T?) {
    val res = block()
    if (res != null) {
        println(res)
    } else {
        println("returned null")
    }
}

fun test() {
    x<Unit> {
        null
    }
}

Kotlin (<1.4) It prints "retuned null Kotlin (>= 1.4) It prints kotlin.Unit The weird part is that

x { null }

works fine. The compiler is able to infer the type to

Unit?

. But I can't write

x<Unit?> { null }

as the type is bound to

Any

which is something we need on Kotlin-Native (unless this has changed too)

isn’t that like

void

fun <T> T.foo(param: T) {

}

suspend fun main() {
	val x = "text"
	val y = 42
	x.foo(y)
}

why does this code compile and run successfully even though x and y are of different types ?

Hey everyone. So we just upgraded our Android project to Kotlin 1.4, and things have gone OK. But we're having this strange problem with Android Studio. The project builds fine, but it's saying it can't find the StringBuilder.appendLine() extension. Yet it sees that StringBuilder.appendLn() is deprecated. and if I ctrl+click into appendLn(), the StringBuilderJVM.kt file clearly has appendLine() in it. Anyone have any ideas? Using AS 4.0.1 and the latest Kotlin plugin, 1.4.10-release-Studio4.0-1 from today.

Hi folks, the Kotlin 1.4.10 is not yet publish at JCenter?

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👋 Is it possible to use @OptIn (i.e

@OptIn(kotlinx.coroutines.ExperimentalCoroutinesApi::class

) for an entire package and sub packages? I’m getting a bunch of warnings in my tests as I’m using experimental

runBlockingTest{}

and I’d love to squash all the warnings in a single place rather than per class annotation.

Since Kotlin 1.4 no longer requires stating the stdlib-dependency in my gradle.kts-file, I removed it, but somehow gradle now imports the 1.3 version of kotlin-reflect (I don't even need kotlin-reflect).

> Task :module-ui:compileTestKotlin
w: Runtime JAR files in the classpath should have the same version. These files were found in the classpath:
    /home/stephan/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib-jdk8/1.4.10/998caa30623f73223194a8b657abd2baec4880ea/kotlin-stdlib-jdk8-1.4.10.jar (version 1.4)
    /home/stephan/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib-jdk7/1.4.10/30e46450b0bb3dbf43898d2f461be4a942784780/kotlin-stdlib-jdk7-1.4.10.jar (version 1.4)
    /home/stephan/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-reflect/1.3.0/6fd129fd9ba8581f2cb9c58bfd431dda4ee0457e/kotlin-reflect-1.3.0.jar (version 1.3)
    /home/stephan/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib/1.4.10/ea29e063d2bbe695be13e9d044dcfb0c7add398e/kotlin-stdlib-1.4.10.jar (version 1.4)
    /home/stephan/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib-common/1.4.10/6229be3465805c99db1142ad75e6c6ddeac0b04c/kotlin-stdlib-common-1.4.10.jar (version 1.4)
w: Consider providing an explicit dependency on kotlin-reflect 1.4 to prevent strange errors
w: Some runtime JAR files in the classpath have an incompatible version. Consider removing them from the classpath

hey, apologies if this has been answered a thousand times, but is there a preferred solution to handling multiple listeners that can be added to one class?

private class MyAdListener(private val listeners: List<AdListener>) : AdListener {
    override fun onAdStarted(adInfo: AdInfo) = listeners.forEach { it.onAdStarted(adInfo) }
    override fun onAdCompleted(adInfo: AdInfo) = listeners.forEach { it.onAdCompleted(adInfo) }
    override fun onAdBreakStarted(adInfo: AdInfo) = listeners.forEach { it.onAdBreakStarted(adInfo) }
    override fun onAdBreakCompleted(adInfo: AdInfo) = listeners.forEach { it.onAdBreakCompleted(adInfo) }
    // etc

is there a method for delegation that works? something like...

private class MyAdListener(private val listeners: List<AdListener>) : AdListener by listeners.each()

[Unsolved] I’m upgrading a project from 1.3.61 to 1.4.10 and IDEA keeps saying that Kotlin isn’t configured in my buildSrc sources, what should I do ?

Not exactly kotlin, but does anyone know how to add a

--compatibility

flag to a Docker Compose run configuration in Ultimate?

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I want to create chatting application same like WhatsApp provides feature with video and audio calling. Any customized SDK available that give above all features. Your help would be appreciated.

I often thought why kotlin doesn't support 'lateinit val', as you know kotlin just has supported 'lateinit var'. My colleague sometime overwrite that variable what I defined. Is there whom can answer for that?

Any idea what can I do to fix this? Or maybe I shouldn’t be using

StateFlow

at all? 🤔

Hey all! Is there a way to run a Coroutine inside a lambda function?

Is there any problem if I put too many functions (might be time consuming) in block init of viewmodel?

how can I rewrite code that looks like this to be more concise so that I avoid having to mention foo.someProperty twice?

fun computeNewValue(msg: String, oldValue: String): String {
    return try {
    	println(msg)
        computeNewValue()
    } catch(e: RuntimeException) {
        oldValue
    }
}

fun main() {
    val foo = Foo()
    foo.someProperty = computeNewValue("Computing foo", foo.someProperty)    
}

Can I check, at runtime, if a cast is valid? I think I'd use a try...catch block in Java; is this the same approach in Kotlin?

what’s the current best Kotlin vs Java article to point people to? 🙂

Hi. There is some interesting discussion in my team about the usage of the functions

also

(https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/also.html) and

run

(https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/run.html). I understand what they are doing but never had the need to use them. Do you use them at all? can you tell a valid case where you used them and it made your code better?

can Libs compiled from 1.4 Mpp Project (android,jvm and js only) be dependencies in 1.3 Mpp (android,jvm and js only) ? I want to know if gradual migration is an option that I have,. By start migrating to some internal libs to 1.4 and move the whole to 1.4 after updating all the dependencies. This might take a while