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announcements

halirutan

03/08/2019, 6:40 AM

Simple question: I need a set of classes that extend (in java) from a base class so that I can iterate over the set and test an object if it

is Base

. Something along

val clazzes : MutableSet< ???> = ...

and then e.g.

clazzes.forEach { c -> if(obj is c){..}}

. How can I do that?

4ntoine

03/08/2019, 12:23 PM

Hey, guys. We’re going to reconsider our system design. Can you point some C++ vs. Kotlin comparisons, benchmarks? Probably including some project management aspects like “coding time” (amount of time required to implement the same functionality), developers costs (average salary), learning curve, etc. Thanks in advance

Siva

03/08/2019, 1:13 PM

Hi friends we are looking for a opensource Kotlin/Java end to end API testing framework any recommendations would be good.

marcinmoskala

03/08/2019, 4:12 PM

There is an error in the IntelliJ template for Android & iOS MPP: Wrapper is missing. Where can I PR it?

amadeu01

03/08/2019, 4:23 PM

guys do you know something like https://github.com/krzysztofzablocki/Sourcery for kotlin?

Gianpaolo

03/08/2019, 4:32 PM

If someone is interested, entire pluralsight catalog for free just for the weekend https://learn.pluralsight.com/offers/2019/free-weekend

😀 1

igor.wojda

03/08/2019, 9:58 PM

What is the easiest way to transpose 2 dimentional list in kotlin?

// now
listOf(
            listOf(1, 2),
            listOf(3, 4)
        )

// want
listOf(
            listOf(3, 1),
            listOf(4, 2)
        )

basher

03/08/2019, 11:15 PM

Will the Kotlin compiler optimize away / remove methods that were generated by declaring a class a

data class

, but ended up being unused?

🇳🇴 1

LeoColman

03/09/2019, 4:11 AM

Some of the issues is "I want this function to be suspendable, but I don't to mark it suspend" -> Inline it so it will use whichever context it is in.

zsmb

03/09/2019, 5:55 PM

Is there a way to mark something with

@Deprecated(level = ERROR, ...)

, or even

HIDDEN

, but still use it in my own code somehow? Seems like I can only suppress the

WARNING

level of deprecation.

Cihan Soylular

03/09/2019, 6:44 PM

Hello guys i’m trying make a exchange application. I will take informations on json file. What is thr best library(s) for working on json? Thanks

groostav

03/09/2019, 10:11 PM

Hey guys, I found a problem with an inspection and I've found the commit that introduced this inspection, but the problem I think is more with how intelliJ is able to implicitly tag some methods with annotations. In my case,

ProcessBuilder.start()

is somehow intrinsically labeled (annotated?) as Blocking (

@Blocking

?), which is simply wrong. I have no idea how to find out where this metadata about ProcessBuilder.start as being a blocking method is coming from, but I'd like to log it as a bug. How might I do that?

kieran

03/10/2019, 10:23 AM

Can someone please point me to an example of a minimal gradle build file that will allow building a shared library for Android and iOS targets, but without including a full blown sub project for each. There won't be any platform specific code. It will literally be the same code compiled for both targets. I've been banging my head against this for days using IDEA templates and official samples as starting points but I'm getting nowhere.

iex

03/10/2019, 12:04 PM

Hello! Is there a way to somehow assign variables in the left side expression of a

when

clause, to be used in the right side?

when {
    toFoo(line) != null -> elements.add(toFoo(line)) // reuse left side result instead?
}

olegstepanov

03/10/2019, 1:53 PM

Hi Can anyone explain why this won't compile:

val String.prop
    get() = object : Supplier<Int> {
        override fun get(): Int = this@prop.toInt()
    }

even though completion actually suggests this@prop?

karelpeeters

03/10/2019, 7:51 PM

You can look into generating the code, eg. using KotlinPoet: https://github.com/square/kotlinpoet. It all still has to be compile-time of course.

Nicole

03/10/2019, 8:09 PM

I think the answer is no, but is there anything like a Union for Kotlin outside of Kotlin native?

LeoColman

03/11/2019, 2:23 AM

Why can't this work:

fun bar(fn: suspend () -> Unit ) { }
fun far() {  
   val fn = {} // () -> Unit
   bar(fn)
}

While I can easily do:

fun far() {
  val fn = {}
  bar {  fn() }
}

sitepodmatt

03/11/2019, 2:42 AM

inline fun bar(fn: () -> Unit ) { 
fn()
}

class InlineSuspendExperiments : StringSpec({

    "test experimenting" {
        runBlocking {
            bar {
                delay(100)
            }
        }
    }
})

reik.schatz

03/11/2019, 8:34 AM

is there a way to generate a sequence but keep the invocation count internal (i.e. not having a mutable

count

as in: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.sequences/generate-sequence.html)

mahdi_perfect

03/11/2019, 11:58 AM

Hi. I've just made a simple markdown DSL, maybe it helps you somewhere. github.com/mahdi13/markdownk.git Also, I would like to know your opinion about this kind of projects, I mean 'converting (almost) everything to kotlin'. Things like android manifest, resources... It could make us reach 100% kotlin projects. Do you think its good? Or wasting time...?

Giorgio Antonioli

03/11/2019, 1:44 PM

Can someone help me with the problem I posted above?

LeoColman

03/11/2019, 2:15 PM

Hey guys, is there anyway to permute all elements in an array with all elements in the other? I'm trying to simplify this:

val foo = firstArr.flatMap { a -> secondArr.map { b -> a to b } }

morbidmerve

03/11/2019, 3:21 PM

Hey guys, I’m trying to figure out how to deserialize/parse an ArrayList from n json string…where the ArrayList object has a generic element type, say

ArrayList<UserActivity>

is the type of the list. anyone have any suggestions on standard practice for ArrayLists? lets say the arrayListString looks something like

{{...somefields...}, {...somefields...}, ... }

where

somefields

are the fields of the UserActivity type.

AndreasBackx

03/11/2019, 3:27 PM

I'm writing a very simple socket server that acts as an HTTP2 client and does some measurements on HTTP2 Server Push for some research as the existing codebase does not have support for a proper HTTP2 client. So I've got an HTTP2 client aspect and socket server aspect in my code. The server listens for some JSON to be sent, parses it, and sends it on a socket that the client is listening on in a coroutine. However the time between sending and receiving the data can be very inconsistent. Because the measurements have to be quite accurate and consistent, I need this to be consistent. (Let's ignore the other speed improvements that could be made for now.) The delay can be almost non existent (1ms or so), 500ms, or almost 2 seconds, see below for some simple logs. Below is also the unparsed JSON data that is sent (it is parsed to data classes and sent over the channel as a List), it is definitely not a large amount of data. What could be the reason for this inconsistency?

[2019-03-11 16:13:33.075] [INFO] Sending items... 
[2019-03-11 16:13:35.746] [INFO] Items received...

[{"segment": 1, "tile": -1, "quality": 0}, {"segment": 1, "tile": -2, "quality": 0}, {"segment": 1, "tile": -3, "quality": 0}, {"segment": 1, "tile": -4, "quality": 0}, {"segment": 1, "tile": -5, "quality": 0}, {"segment": 1, "tile": -6, "quality": 0}, {"segment": 1, "tile": -7, "quality": 0}, {"segment": 1, "tile": -8, "quality": 0}, {"segment": 1, "tile": -9, "quality": 0}, {"segment": 1, "tile": -10, "quality": 0}, {"segment": 1, "tile": -11, "quality": 0}, {"segment": 1, "tile": -12, "quality": 0}, {"segment": 1, "tile": -13, "quality": 0}, {"segment": 1, "tile": -14, "quality": 0}, {"segment": 1, "tile": -15, "quality": 0}, {"segment": 1, "tile": -16, "quality": 0}, {"segment": 1, "tile": -17, "quality": 0}, {"segment": 1, "tile": 1, "quality": 1}, {"segment": 1, "tile": 13, "quality": 1}, {"segment": 1, "tile": 10, "quality": 1}, {"segment": 1, "tile": 9, "quality": 1}, {"segment": 1, "tile": 6, "quality": 1}, {"segment": 1, "tile": 17, "quality": 1}, {"segment": 1, "tile": 14, "quality": 1}, {"segment": 1, "tile": 5, "quality": 1}, {"segment": 1, "tile": 2, "quality": 1}, {"segment": 1, "tile": 16, "quality": 1}, {"segment": 1, "tile": 15, "quality": 1}, {"segment": 1, "tile": 4, "quality": 1}, {"segment": 1, "tile": 3, "quality": 1}, {"segment": 1, "tile": 12, "quality": 1}, {"segment": 1, "tile": 11, "quality": 1}, {"segment": 1, "tile": 8, "quality": 1}, {"segment": 1, "tile": 7, "quality": 1}]

David Cuesta

03/11/2019, 5:56 PM

Hey Guys. I am having a problem with coroutines. I have the next:

GlobalScope.launch {
                CoroutineScope(a.context).launch {
                val b = c.await()
                store(b)
                println("Hello")
            }.join()
        }

where

is an object which contains a Coroutine context and

is a deferred value obtained from a calling a suspend function. It never prints

Hello

because there is a NullPointerException when tries to store

. Anyone knows why is it happening?? My target is to wait until the deferred value a is completed and then store it using the

store

function, which is not a suspend function.

Ruckus

03/11/2019, 6:56 PM

In the docs for
kotlin.math.ceil()
it says it returns:

the smallest double value that is greater than the given value
x
and is a mathematical integer

~~Shouldn't it say:~~

the smallest double value that is greater than or equal to the given value
x
and is a mathematical integer

(similar with
floor
, but obviously the other way around) EDIT: The documentation is actually correct, I just need to learn to read (thanks @karelpeeters)

vkuznetsov

03/11/2019, 6:56 PM

Just curious, is there a simple way to insert X character at every Y positions of the string? Currently doing it by mapIndexed and joinToString, but looking into more accurate solution. Thought about chunked and joining, but I don't want to have X at the end of the String. Example string is 123456 to become 12:34:56

bbaldino

03/11/2019, 7:50 PM

is there a more efficient way to convert 2 bytes to a short in kotlin? i'm worried this is creating a bunch of intermediary types and will be a waste:

fun ByteArray.getShort(byteIndex: Int): Short {
    val b1 = (get(byteIndex) and 0xFF.toByte()).toInt()
    val b2 = (get(byteIndex + 1) and 0xFF.toByte()).toInt()

    return ((b1 shl 8 ) or (b2)).toShort()
}

i could keep static instances of the masks (

0xFF.toByte()

) but i still have to create the Ints which seems like a waste.

bbaldino

03/11/2019, 10:16 PM

is it possible to define a member to look like it is hidden within another? that is, could i define a class like:

class Foo {
  var baz: Int
}

such that callers accessed

baz

by doing

Foo.bar.baz

Title

bbaldino

03/11/2019, 10:16 PM

is it possible to define a member to look like it is hidden within another? that is, could i define a class like:

class Foo {
  var baz: Int
}

such that callers accessed

baz

by doing

Foo.bar.baz

streetsofboston

03/11/2019, 10:21 PM

Not sure why you’d want this, but this would work:

class Foo {
  var baz: Int
}

val Foo.bar get() = this

Now, you can call

val value: Int = myFoo.bar.baz

bbaldino

03/11/2019, 10:23 PM

ah that's pretty slick! don't suppose there'd be a way to do it which would make

baz

only accessible through

bar

the use case is that i've got some properties in Foo that logically would be nested into an inner member, but Foo needs to potentially take action when they're modified (and access Foo data), so was thinking about this as a possible method

and an inner class doesn't feel like the right model, conceptually

streetsofboston

03/11/2019, 10:25 PM

Then an inner class would be good for this. Why don’t you think it’s right to use an inner class?

bbaldino

03/11/2019, 10:29 PM

it feels like this class should be more 'independent' than existing as an inner class, but maybe i'll rethink that.

streetsofboston

03/11/2019, 10:29 PM

interface IFoo {
    var baz : Int
}

class Foo {
    private var baz: Int = 8

    val bar : IFoo = object : IFoo {
        override var baz: Int
            get() = this@Foo.baz
            set(value) { this@Foo.baz = value }
    }
}

fun main() {
    Foo().bar.baz
}

➕ 1

bbaldino

03/11/2019, 10:30 PM

ah that's i think what i was looking for. thanks! i'll weigh that vs the inner class

streetsofboston

03/11/2019, 10:42 PM

Or weirder 🙂

interface InnerFoo {
    val bar : Foo
}

class Foo private constructor() {
    companion object {
        operator fun invoke() : InnerFoo = object : InnerFoo {
            override val bar = Foo()
        }
    }

    private var hiddenProp: Int = 0

    var baz : Int = 0
}

fun main() {
    val foo = Foo()
    foo.bar.baz
    foo.bar.baz = 29
}

😮 1

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