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Hi! I am having logic similar to posted below. Is there any way to do it better?

var a: Int? = null
try {
    a = doSthToGetA()
    useA(a)
} catch(ex: AnyExc) {
    doSthWithA(a)
}

or rather... if another parameter, c, is not null

Hello everyone does anyone know how to enable simple

println()

during a gradle task? (especially a continuous one)

depending on what

foo

actually does

please do chat in a thread

Duplicate class kotlin.reflect.KClasses found in modules jetified-kotlin-reflect-1.0.7.jar (org.jetbrains.kotlin:kotlin-reflect:1.0.7) and jetified-kotlin-stdlib-1.3.70.jar (org.jetbrains.kotlin:kotlin-stdlib:1.3.70)

Can anybody help me figure out this error? I am unable to run tests because of it

"On the Java platform, numbers are physically stored as JVM primitive types, unless we need a nullable number reference (e.g.

Int?

) or generics are involved. In the latter cases numbers are boxed." What does it mean by boxed?

I've just been handed over a problem from a colleague - he's trying to build a Kotlin project with about 650 classes in it, and the gradle build just sits there on the compile Kotlin phase, with the CPU hitting over 500% on the compile process. I'm stumped as to why this is so slow. The classes are all JPA entities. Does anyone have any pointers as to why this might be ?

Hey!

data class Item (val name: String)

sealed class Permission <T> {
    object Create : Permission<Unit>()
    object Edit : Permission<Item>()
}

fun <T> verify(permission: Permission<T>, item: T): Boolean = when (permission) {
    is Create -> true
    is Edit   -> item.name == "editable" // Unresolved reference: name
}

For some reason I expected that when it's known that

T

is

Item

(as it is in

Edit

), then

item

would be properly casted, but I realise that maybe I expected too much. Any idea on how to connect the two (

permission

and

item

)?

Hello, World! I'm finding myself doing this a lot (especially with enums):

val isStateXyz = xx.state in setOf(FOO, BAR, FOOBAR)

Is this idiomatic? Also, I think it may be a bit bad performance... So I was thinking of creating this:

inline fun Any?.equalsAny(vararg objects: Any?): Boolean = objects.any { this == it }

and use it like this

val isStateXyz = xx.equalsAny(FOO, BAR, FOOBAR)

Is it a good idea or should I just keep using

in

? Thoughts?

I have a Repository class that first tries to validate something by going online, but if not available, falls back to an offline validator. I'm using sealed classes to return the state. Right now, return states are all in the same sealed class. I'd like to separate them so only the offline validator can return the offline ones, and only the online one can return online states. But I'd like the Repository to be able to return any of them (whether the validation happens online or offline matters to the upper layers, mainly for displaying to the user). How can I accomplish this?

the short story is that it exists for compatibility with code that came before generics were a thing.

@Mike Conley That's not quite true, erasure was mostly picked for its superiority over reification in many different areas. It would have been possible to have reified generics in Java without breaking any backward compatibility, it just wouldn't have been wise 🙂

Hey, I have a code style question. The code style conventions say "prefer using single expressions". So what can be considered a single expression in Kotlin? I have my understanding but found today that my coworker has a different view and there is no definition in the docs on this as far as I can find. So would like to hear what do you consider a "single expression"

Is there a Kotlin/Java library that can handle this https://stackoverflow.com/questions/1109536/an-algorithm-for-inflating-deflating-offsetting-buffering-polygons

Hello all, I’m trying to do something I usually do on JS that follow something like this:

const myArray = ['1', '2', '3']
let myObj = {
  default = '0'
}

myArray.forEach(elem => {
  myObj = {
    ...myObj,
    [`newProperty-${elem}`] = elem
  }
})

Is there any way to do something like that in Kotlin? Basically, I just need a way to create an object with a variable amount of properties

🛑 Hi does anyone have any good examples of throttling in a REST Api. Extra points if is a http4k based API. 🙏 Server side.

suspend fun main() {
   val items = MarketAPI.getItems()

   for (index in items.indices) {
      println(items[index])
   }

   items.forEach {
      println(it)
   }
}

the return type of

MarketAPI.getItems()

is

List<Item>

where

Item

is a simple data class storing 3 Strings. the first loop works fine, the second one gives me this error: https://hastebin.com/ewuvakikuy how is this possible? how can the way i iterate through the items affect the serialization AFTER it happens? I cant even figure out where exactly it happens. the stacktrace says line 12 in main.kt, however that file only has 11 lines. I set a breakpoint and stepped through, the crash occurs as soon as i reach the second loop. but due to coroutine shenanigans the stacktrace isnt very helpful

Which one is the channel for language questions?

Just published an article on Jetpack compose. About how it works, why it was introduced, what problems it solves, etc. Please go through it whenever you get time and provide your feedback. Thanks https://medium.com/@ajinkyasaswade09/jetpack-compose-what-problem-does-it-solves-110ed9314dbe

Can we make something like try.kotlinlang.com ? and host it to a local server, for fast debugging purposes?

What’s the best way to convert a Map(or MutableMap) into a Data Class?

isnt sealed class take more memory than normal class? considering O(k+m)

Seems like Kotlin extensions was made before Kotlin itself. 🤔 🤔

Anyone knows why I can’t do something like this?

fun myFunction(list: List<String>): List<String> {
    return list.map {
        return it
    }
}

It complains about the return type being a string instead of a List<String>

question on sealed class can i have sealed class with following possibilty for example have a sealed class name Response with following data class Header,Body and Error often ill have Header and Body or Header and Error or Body or Error alone if for example i declare SealeadClass<H,B> if something gone wrong cant pass SealedClass.Error() as response.

We are starting the 1.4-M1 (the first preview version of the upcoming Kotlin 1.4.0) release activities. Please be patient, it will take a bit of time. It will be officially out only after the blog post appears in blog.jetbrains.com/kotlin. In the next couple of days you may see new artifacts appear in various repositories. Since we don’t have full control of all the systems involved, you may temporarily observe and inconsistent state of the 1.4-M1 world. Please don’t be alarmed, the blog post will notify you when we reach a consistent state 🙂 Looking forward to your feedback on 1.4-M1 when it’s ready. Have a nice Kotlin!

Nothing

cant be reified type? why

performance-wise, better a

() -> Unit

or a

Runnable

(on pure kotlin)?