kotlinlang #getting-started

Hey guys, I’ve been using Kotlin for about 5 days now and while I feel pretty comfortable writing it, I can’t help but get the feeling that I’m basically writing Java in the Kotlin syntax. How do I get over this barrier and make sure that I’m actually making best use of what Kotlin has to offer over Java?

techie01

08/02/2017, 10:15 AM

what is difference b/w hashmapOf and mapOf in kotlin

diesieben07

08/02/2017, 11:40 AM

The idiomatic way would be to use the

Array

constructor:

Array(3) { index -> value }

, which initializes the array immediately, so you can have a non-null component type.

👍 1

techie01

08/02/2017, 11:43 AM

how to use gradle for kotlin programming

dekans

08/02/2017, 2:44 PM

maybe

iAmAVar?.let{ it+"XXX" } ?: "XXX"

denis.shakinov

08/02/2017, 4:15 PM

See no point either. @dniHze why wouldn't you just place interface on the same level as your inner class?

oday

08/03/2017, 10:02 AM

where can I see a list of all the functions that work on Collections?

horse_badorties

08/04/2017, 6:36 AM

How do I get to the actual stdlib-sources of - say - the

min()

function in Intellij? When I do

STRG-B

it loads

_Collections.kt

from the

generated

folder of the

kotlin-stdlib-xxx-sources.jar

- which is not the actual source I guess. When I browse the

kotlin\collections

folder instead I find CollectionsKt.class but this does not include the

min()

function. A "Search everywhere" doesn't help either. What is this

generated

folder about anyway? Who generates it and why? 😅

oday

08/04/2017, 10:20 AM

how do I initialize a queue?

techie01

08/04/2017, 10:46 AM

what is meant by asychronous programming

kevinmost

08/04/2017, 9:59 PM

a lint warning for `IntRange`s where the lower bound is higher than the higher bound might be useful

➕ 1

voddan

08/05/2017, 6:06 AM

@horse_badorties @johnaqel This limitation of

..

is made so to emulate the traditional

for

loop. In a code

for(int i = A; i < B; i++){}

nothing happens if

is greater than

. This is how programmers are accustomed to think about iterations. If the

..

loop worked both ways, the number of bugs would be colossal.

oday

08/05/2017, 9:17 PM

also, whoever linked me to this video

https://www.youtube.com/watch?v=AhA-Q7MOre0&list=PLtRrDEpV3zktLTZlkx0CPqyIYQ4Z9m7v0&index=5▾

it’s way too complex, is there a better introduction example for functional programming for Kotlin?

danneu

08/05/2017, 11:12 PM

anyone know what i'm talking about and what i'd look into for changing it so that intellij waits til i tell it to build or at least waits til i save build.gradle?

oday

08/06/2017, 11:18 AM

how would I go about implementing this

benleggiero

08/06/2017, 10:33 PM

Why won't this compile?

open class Queue<Element>(protected var backingList: MutableList<Element> = mutableListOf()) {
    fun listValue():List<Element> = List(*(backingList.toTypedArray().copyOf()))
}

Error:

Error:(44, 56) Kotlin: Cannot use 'Element' as reified type parameter. Use a class instead.

techie01

08/07/2017, 11:36 AM

how to add two nullable values

techie01

08/07/2017, 2:21 PM

how to print list of collection names by using kmongo

:stackoverflow: 4

stefano.maffullo

08/07/2017, 5:09 PM

I think you can override it and make it return every string you want 😅

eldamsheety

08/08/2017, 1:05 PM

Which one should I learn, JavaFx or TornadoFx?

techie01

08/08/2017, 2:23 PM

how to get it for free

horse_badorties

08/09/2017, 7:44 AM

is there a

java.util.EnumSet

equivalent in Kotlin? If not (how) can I use it with a Kotlin

enum class

v79

08/09/2017, 9:19 AM

Are data classes any lighter on the JVM to instantiate and use? Or are they just a programmer's convenience?

infini

08/09/2017, 1:00 PM

your brackets look off - what happens if you do mode?.equals

chet

08/10/2017, 6:36 AM

Hi all, I'm kotlin beginner, regarding the "when expression", is it just a powerful switch case, or does pattern matching also? You can only check types/values or you can destructure variables also? Use of when expression with sealed classes almost look like it may be some form of pattern matching expression?

brokenpipe

08/10/2017, 8:14 AM

Hi, how can I define secondary constructor calling it's super constructor? eg.

mcscruff

08/10/2017, 10:46 AM

im a little stuck, i have a mutable map with Names as a key and address's as a value, is it possible to "get" the key and value at any given index. For example, if i wanted to know the 6th in the map

mcscruff

08/10/2017, 11:05 AM

also, is there plans to build a ChromeOS / Android version of IntelliJ

techie01

08/10/2017, 11:59 AM

can we convert json to xml

ar-g

08/10/2017, 12:51 PM

How to define object inside sealed generic hierarchy?

sealed class PaginationViewState<T> {
    object LoadingFirstPage: PaginationViewState<T>()//doesn't work
    object LoadingPage: PaginationViewState<T>()//doesn't work

    data class DataLoaded<T>(val data: List<T>): PaginationViewState<T>()
    data class DataLoadedFromCache<T>(val data: List<T>): PaginationViewState<T>()
    data class Failure<T>(val e: Throwable): PaginationViewState<T>()
}

Title

ar-g

08/10/2017, 12:51 PM

How to define object inside sealed generic hierarchy?

sealed class PaginationViewState<T> {
    object LoadingFirstPage: PaginationViewState<T>()//doesn't work
    object LoadingPage: PaginationViewState<T>()//doesn't work

    data class DataLoaded<T>(val data: List<T>): PaginationViewState<T>()
    data class DataLoadedFromCache<T>(val data: List<T>): PaginationViewState<T>()
    data class Failure<T>(val e: Throwable): PaginationViewState<T>()
}

marstran

08/10/2017, 12:54 PM

You need to specify a

for your objects.

By the way, after Kotlin 1.1, you don't need to nest the classes and objects inside the sealed class. They just have to be in the same file.

ar-g

08/10/2017, 12:55 PM

no, type parameters not allowed

marstran

08/10/2017, 12:56 PM

The

has to be an actual class/interface here:

object LoadingFirstPage : PaginationViewState<T>()

No type parameters allowed? What do you mean? You have specified

PaginationViewState

with a type parameter.

ar-g

08/10/2017, 12:57 PM

not allowed in this statement

object LoadingFirstPage<T>: PaginationViewState<T>()

marstran

08/10/2017, 12:57 PM

That doesn't work because there is only one instance of

LoadingFirstPage

. It can't take parameters.

Maybe

LoadingFirstPage

should be a class then?

ar-g

08/10/2017, 12:58 PM

that is what I did😀

marstran

08/10/2017, 1:09 PM

It looks like that should be the correct solution for you looking at your example.

is the type of data that the view state holds, so

LoadingFirstPage

and

LoadingPage

are classes, not objects.

I see you are writing on the StackOverflow post that using

Any

is what you were looking for. I really don't think you should do that. You are losing type information that you don't have to lose.

👍 1

ar-g

08/10/2017, 1:21 PM

yes, it is meaningless since I can't define class with desired type

PaginationViewState<AdModel> =PaginationViewState.LoadingFirstPage

. I'll stick with regular classes probably

marstran

08/10/2017, 1:46 PM

You can still have (and you should have) a sealed class hierarchy though.

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