If I have a

MutableList

, and I expose it to another function with just the

List

interface, can that function cast it to

MutableList

? At what point is something cast-able to its original type? I'm not new to generics but I haven't thought about that before.

Hey In my library (that will be distributed) I have simple Kotlin data class where some of the properties are nullable

// Kotlin class
data class Test(
val name: String,
val lastName :String?
)

// Generated Java class src
public final data class Test public constructor(name: kotlin.String, lastName: kotlin.String) { 
}

Since this class will be also used from Java is there any way to include

Nullable

and

NonNull

annotations in generated the code for the properties? Something like this:

// Generated Java class src
public final data class Test public constructor(@NonNull name: kotlin.String, @Nullable lastName: kotlin.String) { 
}

(I mostly care about

NonNull

): The main drive for this behaviours is that now I can create new instance of

Test

class from Java and pass null values

new Test(null, null)

without any indication that this is wrong/undesired usage- I believe with annotations IDE would display error/waring 🤔

is there a better way to divide ints and round down to an int than this

floor(int1.toDouble() / int2).toInt()

congrats @elizarov 👏

The Kotlin community is what drives the Kotlin project forward and you are the ones who we, in the Kotlin team, all ultimately work for. Thank you for your love for Kotlin ❤️

Is there a Kotlin equivalent for a Swift

DispatchQue

? I have a

MutableMap<T,T>

and I want to make operations done to it thread safe. So far I just wrap accesses to it in:

val lock = Any()
synchronised(lock) { map.doTheThing() }

Is this fine?

First time creating an Android project in 4.2. I have a MainActivity in which I want to immediately launch another Activity tht I created that has my Compose views built. I know I can change the Manifest file, but I want to understand how to move from MainActivity to another activity. THANK YOU IN ADVANCE

In this example

foo

is not being smart casted to non-null even tho it cannot be null in that else block. Shouldn’t the compiler be smart enough to infer this?

class Foo(val str: String? = "")
val foo: Foo? = null
if (foo?.str.isNullOrBlank()) {
   //...
} else {
   println(foo.str) // doesn't compile. foo is not smart-casted to a non-null type
}

Btw if the condition was

foo?.str == null

, this would compile. so it’s not impossible to “backtrack” from

str

to

foo

in this case

Hi! I have a nullable

val property: String?

in

src/main

and then in

src/test

I have

if (property != null) property.length

and this gives an error that

property

cannot be smart-casted, because it's defined in a different module. But it's the same [gradle] module! Also I have just moved this class + its test from another module where there was no such error. Why can this happen? Drives me nuts. Tried to compile outside an IDE from console, same errors...

Naming issue help I have a shared library across multiple apps. Lets say it provides

Authenticator

class which has

login()

function Now, app B needs logout as well, so it extends Authenticator and adds

logout()

functionality. How would you call such type? 1) If I were to take inspiration from the way List interface looks I'd call it

LogoutableAuthenticator

But such name looks silly for app B developers, as they only use a

Authenticator

which has both login and logout functions 1.5) Give it app name prefix like

AppBAuthenticator

. Also feels silly. All app B types then should have this prefix 2) Or, design it backwards, leave leaf implementations prefixless, so app B has Authenticator but it extends

BaseAuthenticator

. But this again looks stupid in shared code 3) Name them both Authenticator and let just the package name be different

If somebody is online to help 😅😁: https://stackoverflow.com/q/64924393/11377112

What's the correct way to instantiate a class using the reflections (KClass) with primary constructor? Assuming we know the type and number of parameters.

Is is a good idea to use

GlobalScope

in a singleton class?

do Closures close over Sychronized monitor blocks? I declare a

FixedThreadPool

executor within a synchronized block, and I pass in a ThreadFactory Lambda fun; when the threadfactory function is subsequently evaluated, will the Monitor lock be acquired? (I am hoping/expecting not - otherwise I would put the sychronized inside the ThreadFactory fn)

Hi All. I’m trying to write a KSP compiler plugin. The problem is that i need to depend on classes that live in .aar files (ie, firebase-config). Is this even possible? I’m adding the dependency to my annotations module which has the kotlin.jvm plugin setup. However, because it’s an aar, i can’t import the classes. Anyone ever tried to do this before?

Hey folks, we’re using Kotest and was wondering if there’s a library or a way of writing fixtures that other folks seem to like and enjoy?

Hi all, diktat 0.1.5 was released. Diktat is awesome kotlin linter with hundreds of inspections (unique inspections, that are missing in ktlint and detekt) and autofixers, and it’s own strict code style codestyle. And we need your help! We need stars on github to attract more developers to the project. Please support us with your star: https://github.com/cqfn/diKTat

This just feels spammy.

i have a Builder class with a bunch of functions for various types

.with(key: String, value: String)

,

.with(key: String, value: Boolean)

. i'd like to be able to call these functions conditionally on the call site. i can't think of anything better than simply adding a param

.with(key: String, value: String, shouldUse: Boolean)

to determine if a value should be used internally by the builder if

shouldUse

is true

Is there a way to make this type of inference work?

Le canal saint martin?

is there a cleaner way to do this?

val filteredMap: Map<String, B> = someMap.filterValues { value -> value is B } as Map<String, B>

because the unchecked cast is marked as warning

I'm using latest version of Intellij EAP, but the IDE can't find the latest version of kotlin(1.4.20) plugin. version found: 1.4.10 (203-1.4.10-release-IJ5981.20) Do I have to manually install the plugin or add any repository?

Hey guys, is it possible, that data class could generate StackOverFlow while compiling? After implementing the OpenApiGenerator for a strange Server API, i got multiple generated data class with > 200 fields. Don't ask for the reason of such apis... No possibility to change it for now... While app:compileDebugKotlin a crash... Haven't seen such an error before. Any ideas? Kotlin 1.4.10 with enabled Jetpack Compose for Android I replaced the classname with xx.xxxx.xxxx.xxxx.xx.xxxx.Xxxxx

hello, anyone has fail compile issue with the new

kotlin 1.4.20

and

Optional<V>

Type mismatch: inferred type is Optional<V!!> but Optional<V> was expected

the same code compile ok in

kotlin 1.4.10

fun first(vPredicate: (V) -> Boolean): Optional<V> {
        val v: V? = firstOrNull(vPredicate)
        return if (v == null) {
            Optional.empty()
        } else {
            Optional.of(v)
        }
    }

the errored line is the one that return

Optional.empty()

Kotlin 1.4.20 Released Kotlin 1.4.20 is here with new experimental features for you to try. Being open to community feedback is one of the Kotlin team’s basic principles, and we need your thoughts about the prototypes of the new features. Give them a try and share your feedback on Slack (get an invite here) or YouTrack. Here are […]

when using:

fun XMLStreamWriter.writeStuff(action: XMLStreamWriter.() -> Unit)

how does Kotlin know where it takes the this from?

This message was deleted.

is there a way to use a kotlin flow retry operator without the source throwing an exception? as in if the source returns some value retry the original flow