hey! I'm trying to write a generic function to set a default value on a nullable property of an immutable object and I have two obstacles: - can I constraint a type so it is a data class (implements a copy constructor)? - can I address the right property in the copy constructor using the KProperty? This is what I have so far:

fun <T: ???, R> T.setDefault(prop: KProperty1<T, R>, defaultValue: R): T =
        prop.get(this)?.let { this } ?: copy(??? = defaultValue)

P.S. maybe this I'm trying to do is stupid/not worth it, feel free to point it out

Is there a documentation about which

stdlib

dependency does what? For example, should I use

stdlib-jdk8

for an Android lib/app?

What's the best way to go from a

Stream<T>

to a typed array of

Array<T>

? I need to convert a

Map<String,String>

to an

Array<Pair<String,String>>

. I've done this as follows:

val array: Array<Pair<String, String>> = myMap.entries.stream().map {
        Pair(it.key, it.value)
    }.toList().toTypedArray()

Is that the most efficient way? It seems like converting to a

List

first and then to the (typed)

Array

has an extra step. But I'm not seeing any other way to go from the

Stream<Pair<String,String>>

coming out of the

map{}

function to a typed

Array<Pair<String,String>>

(since

Stream.toArray()

would give me an untyped Array of

Array<Any>

).

i'm having some java interop issues with

@Throws

The API

interface StormcrowBase {
   @get:Throws(Exception::class)
   val featureNames: ArrayList<String>
}

Java call site

try {
                features = stormcrowBase.getFeatureNames();
            } catch (Exception e) {
                e.printStackTrace();
            }

The error I'm getting is

Exception is never thrown in the corresponding block

. Any ideas?

Hello everyone, Someone can tell me wich is the best way to create a singleton, I had read something about "by lazy" but also another property like by DelegatesExt.notNullSingleValue()

If I want to get something out of an http session, it can be either null, or of a particular type, which I have to cast to. So to cope with this I've coded something like this:

val tokenMap = (session.getAttribute(sessionAttributeName)   ?: mutableMapOf<String, AgedToken>()) as MutableMap<String, AgedToken>

Which means I do get a compiler warning "Warning:(39, 55) Kotlin: Unchecked cast: Any to MutableMap<String, AgedToken>" Is there any way I can do this better and get rid of the warning ?

Is anyone here successfully generating kotlin data classes from json schema in a pipeline? i.e. not using an android plugin

Can cast operators be overloaded to support safe casting of known types (conditionally)? I have a lot of factories for wrapper types (do some additional validation on the input, and return

Type?

), but it would be kind of cool to replace those with

as?

directly.

Oh boy, update is coming, anxiously waiting the changelog and announcement.

My Intellij is already installing it. 😅

Is there a changelog for Kotlin 1.3.5? Curious if the new type inference engine is used in the compiler now

Working on an improved Kotlin-to-Java converter.

This should say "Java-to-Kotlin". Hopefully someone from JB can fix that.

I’m implementing this https://www.rabbitmq.com/passwords.html#computing-password-hash, how can I generate this as a byte array in kotlin?

908D C60A

note: I don’t mean generate a salt I mean literally these bytes, I’m trying to test my algorithm and see if I get the same base64 encoded string

I'm really struggling with something - I'm working on the bazel rules, but as of 1.3.40, if you pull in any version of kotlin after 1.3.31, code that compiles perfectly well under the existing rules breaks on "internal". But I cannot find, for the life of me, any changelog information relating to the compiler enforcing anew, or more strictly, module-membership. Did something change between 1.3.31 and 1.3.40 that caused this increased strictness? It's literally a matter of same code, same build rules and infrastructure, swap out which version of kotlinc.zip it uses, and it builds or doesn't, if it's at or post 1.3.31 respectively. Any ideas? Any changes that didn't make it into the changelog, but which anyone knows about?

This message was deleted.

Do you need the reified though? Can't you get the class from the instance at runtime like

when(defaultValue::class)

or something like that

Is there a way to use kotlin scripting engine from android that has no javax.scripting ?

Are there any cases where a

val

might be

const

but it is useful not to make it

const

?

if (x != null) {
    y = x
}

is there a shorter way to do this? I recall there being some way by using the

?

operator but im not sure if that was in kotlin or another language

Unfortunately OpenCV only has full access with c++ header, is there any solution can I access c++ header with cinterops to generate klib?

Just found that

internal

kotlin classes are

public

to java code. How to write kotlin library without exposing all classes to java?

Can someone please tell me how I can see declarations of reflection types like

KFunction

and

KSuspendFunction1

? I have imported imported

kotlin-reflect

but I have to manually import them and IDE inspection tools like go to declaration and search in path can't find their declaration

is there any work on a Kotlin interpreter (for faster repl, better scripting support, etc)

Anybody also wondering about this topic? When does a when expression in kotlin need to be exhaustive and when does it not? https://github.com/Dobiasd/articles/blob/master/when_does_a_when_expression_in_kotlin_need_to_be_exhaustive_and_when_does_it_not.md

words is CharSequence

returns

false

. Isn't it wierd?

The different order of the interfaces {Appendable, CharSequence} doesn't group the compilation targets together.

Can anyone please help me with this? I am trying to emulate

readLine

function from stdlib which yields each line in the multiline text block. This is supposed to act just like

readLine

but reads from a fixed string instead of stdin. Here is how I'm trying to make it work: https://pl.kotl.in/f-ayPvSC-

Given a DSL that is defined by an external project (Gradle in my case), is it possible to define an extension function

fun String.someExtensionFunction() = "Hello World"

that would be usable only from the right extension block?

dependencies { // this is Dependencies
    ....
}

That seems impossible because it would require to define the function having two receivers,

Dependencies

and

String

what is the purpose of

object

? isn't it basically same as top level members in a separate package?