kotlinlang #announcements

data class MyDataClass(
        val myMap: Map<Int, String> = mapOf()
)

fun addElementToMyDataClass(myInstance : MyDataClass, key : Int, value : String): MyDataClass {
    val mutableCopyOfMap = myInstance.myMap.toMutableMap()
    mutableCopyOfMap[key] = value
    return myInstance.copy(myMap = mutableCopyOfMap)
}

01/19/2018, 5:24 PM

val fullTariffList = arrayOf("customer", "reseller", "vendor").flatMap { type ->  testTariffList.map { it.copy(type = type) } }

:kotlin: 1

➕ 1

katien

01/19/2018, 8:39 PM

it's part of kotlintest

vlad

01/19/2018, 11:00 PM

can default function arguments be lazily computed expressions?

cedric

01/19/2018, 11:07 PM

Not without turning them into a lambda

Yash Jahit

01/19/2018, 11:37 PM

@Shawn I dont mean to hurt nor disrespect anyone. If i am wrong then ill admit it. If you think i did ask for the code, then i am sorry to anyone. Its just..anyway personal problems. Sorry again

akritrime

01/20/2018, 6:48 AM

Hey I am a noob learning Kotlin and I don't know Java. Can someone help me understand the difference between sealed classes and enums? Am I right in assuming enums are like singleton sealed classes?

shawwn

01/20/2018, 9:16 AM

It will only take about 60 seconds

elect

01/20/2018, 10:20 AM

how to check if an

ArrayList<Long>

is in ascending order? Something available in stlib?

tipsy

01/20/2018, 11:16 AM

i have a pretty long questions about the different ways of calling a java method from kotlin, so i'm going to nest it into a thread

fabricio

01/20/2018, 11:25 AM

when (obj) {
    null -> println("is null")
    else -> println("is not null")
}

I couldn't figure out how to check for not null instead.. is that possible? like

!null ->

😄

Les

01/20/2018, 11:41 AM

I was looking at Kotlin source. I found code

contract { callsInPlace(block, InvocationKind.EXACTLY_ONCE) }

Where does

contract

come from? What does this code do?

phantom

01/20/2018, 3:41 PM

one question, why does javascript has .jsx, typescript .tsx, but kotlin has no react support like .ktx?

👍 2

👎 1

Dmitry Kandalov

01/20/2018, 10:50 PM

Is there a way to call extension function with fully qualified name?

alexcouch

01/21/2018, 11:37 AM

I have a question about local variables. So since you can declare a local variable without an initializer which basically makes them marked with lateinit by default right? And if it doesn't have nullability, and when I try to use it after init'ing it with a conditional, (like the example below), and then I wanna try using it afterwards, then, even tho it's not nullable, it, by default, is null right? And if that's the case, then how can I check if it is init'd even though it's nonnull? Here's an example:

fun ArrayList<ItemStack>.tick(){
    var emptyStack: ItemStack
    for(stack in this){
        if(emptyStack == null) {
            if (stack.isEmpty) {
                emptyStack = stack
            }
        }
    }
}

Ayden

01/21/2018, 12:20 PM

Does Kotlin allows us to use the code like this?

// numberList: 1, 2, 3, 4, 5, 6

numberList.contains(1,2,6)

amanda.hinchman-dominguez

01/21/2018, 4:16 PM

@Ruckus but it allows you to use Java types as well, which does present a risk for nullable types

Ruckus

01/21/2018, 4:21 PM

You could do

int("whatever") ?: default

fabricio

01/21/2018, 5:44 PM

can anyone help me understand

.let .also .apply etc

extension methods?

:google: 1

Olekss

01/21/2018, 7:00 PM

so is there whay how to get from Method to Function1 ?

pablisco

01/21/2018, 8:02 PM

Didn't know where to ask this. O was looking at the code for the Kotlin Conf app and I don't see how the iOS app uses the code from

Common

is there any blog post or guide on how it works?

dave08

01/22/2018, 8:12 AM

What's the accepted practice for not found situations in repos and apis? Say I have

userRepo.getUser(userId)

and it wasn't found, should it return null, throw a domain exception (NoUserFoundException) or have a sealed class with a null object? (I'm using coroutines, not Rx...)

👍 1

bj0

01/22/2018, 11:29 PM

set doesn't return a value, why not just

set(value) { baz.bar = value }

Ruckus

01/22/2018, 11:48 PM

@benleggiero I think what you are looking for is the elusive "just do what I mean" operator. I heard they're adding it to JavaScript.

raulraja

01/22/2018, 11:57 PM

But where does

baz

come from?

aoriani

01/23/2018, 1:26 AM

How much compatible Kotlin generics are with Java ?

sealed class NetworkResource<out ResponseType, out ErrorType> {
    class Loading<out ResponseType, out ErrorType> : NetworkResource<ResponseType, ErrorType>()
    data class Success<out ResponseType, out ErrorType>(val response: ResponseType) : NetworkResource<ResponseType, ErrorType>()
    data class Error<out ResponseType, out ErrorType>(val error: ErrorType) : NetworkResource<ResponseType, ErrorType>()
}

class NetworkObserver<ResponseType, ErrorType> : Observer<NetworkResource<ResponseType, ErrorType>> {}

When I use it from Java I'm getting

incompatible types: <anonymous NetworkObserver<Object,String>> cannot be converted to Observer<NetworkResource<Object,String>>

. However if I am remove

out

from NetworkResource it works for Java, but it messes type inference in Kotlin.

alexanderUV

01/23/2018, 6:06 AM

is there a kotlin-native channel? I don't see one

edwardwongtl

01/23/2018, 10:32 AM

And the compiler knows exactly how many child class it has

poohbar

01/23/2018, 2:00 PM

Is there a solid step by step guide on how to solve this build error?

Runtime JAR files in the classpath should have the same version.

For the life of me I can't find what's pulling in the wrong version of stdlib.

marcinmoskala

01/23/2018, 4:05 PM

Looks like there is something wrong with https://try.kotlinlang.org/ It is loading definitively on my machine and it displays a lot of errors