what does this

handler: (key: K) -> V?)

means In the following function

fun getOrPut(key: String, handler: (key: String) -> V?)

i thinks

handler

is something likes the arguments name, so what are the rest? is it a lambda ?

Ok, I'm new to Kotlin, so just want to validate some info. My goal is to write a library (or SDK/API) in Kotlin Multiplatform that will be consumed by native mobile clients in either Android (Kotlin, Java) or iOS (Swift, Objective-C). From what I understand, the generated SDK artifact would be a .framework file for iOS consumers and a .jar file (or .class files) for Android consumers, is this correct? Thanks in advance!

Is there a kotlinfied

Character.getNumericValue()

?

Is there something like Pythons 3.8 f-string = syntax in Kotlin? I.e. with

val foo="bar"

I would like to not have to write the

foo=

part in

"foo=$foo"

in order to get the string

foo=bar

, but, like in Python, perhaps like this instead:

"${foo=}"

but that gives me compilation errors in Kotlin version 1.3.41 (JRE 1.8.0_221-b11)

Noob question #237: Can you write an MPP library targeting iOS (among others), so that it would output a .framework file, using IntelliJ for Windows?

Hey, I'm working on a project that is a addon to a java program, to make it work I have to shade in kotlin-stdlib but that makes the output jar come out to ~8mbs, anyone know a way to only shade in whats actually used? Thanks for the help using maven shade plugin

Hi, is there some collection api that trims a mutable list to a size? I know

take

but that creates a new list

but it should be maybe more efficient, i.e. just trim the underlying array

that has to be super ineffecient, right?

I should mention this is using Kotlin-1.3.0

I need some advice for my following code.

import java.time.Duratio

class SimpleObjectCache (val cacheDuration: Duration)  {
    private val cacheManager = if (cacheDuration.getSeconds().toInt() <= 2147483647) SimpleObjectCacheManager(cacheDuration.getSeconds().toInt()) else throw IllegalArgumentException("cacheDuration Int value is out of range")

It is simple, i hope you got what i m doing is.

cacheManger

is too long right? 😁 Is there any better way? 🤔

Read through Kotlin's docs, can you recommend any other resource that can take me indepth Kotlin? Thanks!

I am curious, in this code:

fun String.asIndex(): Int = withIndex().sumBy { ... }

Why does the call to withIndex() not need use "it" or "this" ? <<I am newbie, obviously!>>

to*

I’m trying to count the diffs in two equal-lengthed strings. My approach is to reduce one string into an int, using the index to compare chars in the other string. Maybe I’m just thinking about this too much like JS?

str1 = "ABC"
str2 = "ABB"
diff = 1
// JS
str1.reduce((accumulator, currLetter, index) => {
      if (currLetter !== str2[index])  return accumulator + 1
}, 0)

Is this a kotlin-y way to approach the problem or am I being a dingus?

I’m thinking functional style and, rather than overwriting the current state of my object, a colleague suggested I append the latest state to a list, so I never overwrite/throw away information.

:thread-please: Use threads, please

I’m a longtime Java developer and have always wanted to build Android apps but never seem to get the time. Also want to learn more about Kotlin. Can I kill 2 birds with one stone by starting off using Kotlin for Android apps to keep my interest going? Or should I start with a more general overview of the programming language first to avoid missing fundamentals?

Writed this code but looks just like java with different sintax, what would be a kotliner way to write such function?

fun StringValues.getUuidParam(name: String): UUID {
    val id = getAll(name)?.firstOrNull() 
    if(id != null)
        try {
            return UUID.fromString(id)
        } catch (e: InvalidArgumentException) {
            httpException(developerMessage = "Parameter $name does not contain a valid UUID")
        }
    else
        httpException(developerMessage = "Required param $name is not present")
}

Why does this code work

fun String?.whenNotNullOrEmpty(callback: (String) -> String?): String? {
    return if (this.isNullOrEmpty()) null
    else callback(this)
}

but this doesn’t ?

fun String?.whenNotNullOrEmpty(callback: (String) -> String?): String? {
    return if (isNullOrEmpty()) null
    else callback(this)
}

I still find myself doing something like:

if (viewModel.value?.items()?.subItems != null) {
    //Do my thing
}

I don't think this is bad because it's straight forward. As long as that statement is not null I want to execute some code. Is there a more idiomatic way of doing this?

Is there a way to access an instance variable from an inner class of a sealed class? Here’s a code excerpt:

class NearbyConnection{

    var connectionsClient: ConnectionsClient = Nearby.getConnectionsClient(context)
    
    public sealed class ConnectionState(val name: String) {
        inner class Authenticating: ConnectionState("authenticating") {
            fun accept() {
                connectionsClient.acceptConnection(neighborId, payloadCallback)
                updateState(ConnectionState.Connecting(neighborId, neighborName))
            }
        }

I am getting the error “unresolved reference connectionsClient” within the function.

I am quite new to this slack as well as Kotlin. In this platform we can ask doubts related to the code but can anyone tell me that from where should I start. I know learning any coding language has endless concepts but till what I must do to be a successful kotlin developer ?

I’m trying to use reflection to get the name of classes extending a sealed class, but I always get the name of the sealed class (

ConnectionState

). Here’s my code:

public sealed class ConnectionState() {
        var name = ConnectionState::class.simpleName ?: "null"

        object Isolated : ConnectionState()
        object Advertising : ConnectionState()  
        object Discovering : ConnectionState()
   }

Any advice?

This message was deleted.

are top-level variables outside of a class referred to as "properties"?

val a
get() = Random().nextInt(10)

Is this the only situation a

val

can return a different value each time it is accessed? (obviously the Random function is replaceable)

also, how do you access a top-level variable outside a class when there is another one with the same name inside the function