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announcements

user

10/02/2018, 9:22 AM

message has been deleted

🔥 5

Fré Dumazy

10/02/2018, 11:50 AM

Can I build my kotlin projects with jdk11 on my machine? or does it only work with jdk8

pablisco

10/02/2018, 12:29 PM

In Kotlin, do we have a way (or a KEEP) to be able to define a Java Method as a getter without the prefix

get

miha-x64

10/02/2018, 8:31 PM

Why

kotlinc

generates

somePropertyName$annotations()

with annotations instead of putting them onto the backing field?..

Hexa

10/02/2018, 11:56 PM

does anyone know how to fix

Error:(33, 76) Kotlin: Unresolved reference: messageIndex

in this line here? https://gist.github.com/rinnegan/878a8451bbae54441a588e75a5acbacd#file-group-by-messageindex-L33 . I want to group by

MessageIndex

. Code does not work if I remove

val messageIndex: MessageIndex

from this class

data class MessageSender(
        val message: String

        //, val messageIndex: MessageIndex
)

hamid.s

10/03/2018, 7:02 AM

Do we need {} in if? When it is only one operator, should I add {} after if? Here is a sample: if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) { window.statusBarColor = Util.getColor(R.color.accent_color) }

BorzdeG

10/03/2018, 11:59 AM

Tell me, what is not configured in the project https://github.com/BorzdeG/example-hello-multiplatform? When I run “./gradlew clean check” I get the error:

> Task :hello-other-common:jar
e: .../hello-other-jvm/src/main/kotlin/hello/other/jvm/HelloOtherData.kt: (3, 21): Unresolved reference: HelloCommonData
e: .../hello-other-jvm/src/main/kotlin/hello/other/jvm/HelloOtherData.kt: (5, 48): Unresolved reference: HelloCommonData
> Task :hello-other-jvm:compileKotlin FAILED

At the same time, there are no errors in IDEA - only during the execution of the code.

Hamza

10/03/2018, 2:11 PM

im sick of maven now so often whenever i set a program, it can’t read my dependencies. it happens so often and im so annoyed. why does this happen? This happens more often than not, im not sure why. someone please help me resolve tihs issue permanently

:gradle: 5

hallvard

10/03/2018, 2:34 PM

I'm multiplatforming (and it seems to work!), but I would like to declare an `expect`ed init block and can't seem to get the syntax right. Anyone care to give me an example or point me in the right direction?

Slackbot

10/03/2018, 3:32 PM

This message was deleted.

Hexa

10/03/2018, 3:34 PM

does anyone know how to fix this syntax error? I want to alter the structure of the first map so that it returns

List<Pair<PublisherMessage, deviceType>>

. It currrently only returns

emailMesssages: List<MessageSender>

wei

10/03/2018, 4:44 PM

I have a list of keys

keys

and another map of key -> value

map

, whose keys are a subset of

keys

and whose value is either

SOFT_DELETED

NOT_DELETED

. For example:

val keys = listOf("key1", "key2", "key3")
val map = mapOf("key1" to "SOFT_DELETED", "key2" to "NOT_DELETED")

I need to combine

keys

and

map

to generate another map

finalMap

, whose keys will contain all keys from

keys

that are not in keys of

map

with values of

DELETED

and keys of

map

that has a value of

SOFT_DELETED

. In the above example, I’d have:

val finalMap = mapOf("key1" to "SOFT_DELETED", "key3" to "DELETED")

I can think of mapping over

keys

and check each key against

map

and generate

finalMap

, like:

val finalMap = keys.mapNotNull {
  when(map[it]) {
    "SOFT_DELETED") -> it to "SOFT_DELETED"
    null -> it to "DELETED"
    else -> null
  }
}

Is there a more idiomatic way in kotlin to do this?

karelpeeters

10/03/2018, 4:55 PM

keys.associate { it to "DELETED" } + map.filter { (k, v) -> v == "SOFT_DELETED" }

Mike

10/03/2018, 5:47 PM

Question regarding Null annotation support. When originally announced (https://blog.jetbrains.com/kotlin/2015/04/upcoming-change-more-null-safety-for-java/), support for javax.validation.constraints was listed. In some generated code, it has the javax.validation.constraints.NotNull annotation BUT IntelliJ and Kotlin aren't correctly detecting it. If I modify the generated code to use either org.jetbrains.annotations.NotNull or org.springframework.lang.NonNull or javax.annotation.Nonnull, they all work as expected. Was it decided to not include javax.validation.constraints in the list after all, or have I potentially found an issue? I haven't been able to find anything concrete on this topic so hoping someone here can provide some clarity.

Slackbot

10/03/2018, 6:10 PM

This message was deleted.

:stackoverflow: 1

ValV

10/03/2018, 7:44 PM

Why equality checks are preferable over elvis operator in case, when a boolean variable is nullabe? E.g.

val parameter: Boolean? by param()
if (parameter != false) ...

instead of

val parameter: Boolean? by param()
if (parameter ?: true) ...

👍 2

jdemeulenaere

10/03/2018, 7:56 PM

It would be nice to have official support of Bazel to compile Kotlin, in my experience it makes building and testing much faster than with gradle. I know there are some already some rules by the Bazel team but I don't think they support multiplatform targets and the different compiler plugins. (Just a thought 🙂 )

➕ 1

digitalsanctum

10/03/2018, 10:01 PM

Any recommendations for a library that makes creating a cli with Kotlin easy? I'm aware of a few in Java land but looking for alternatives

Viral Thakker

10/04/2018, 6:21 AM

Hi everyone, Can anyone tell me why should we use kotlin instead of Java in business application?

molikto

10/04/2018, 7:15 AM

I found I write code like this very often, a private mutable object and a public facing immutable api. is anyway to do it more elegantly in Kotlin? does it worth as a syntax sugar?

👍 1

qwert_ukg

10/04/2018, 8:34 AM

I have a builder for my HTML layout and use it in my controllers. I want encapsulate a

render

function into my API file and don't want to provide an possibility to call it from builder

Bernhard

10/04/2018, 10:37 AM

what annotation target is equivalent to the java TYPE_USE

bod

10/04/2018, 11:55 AM

Hello, World! I’m in a

when (e)

, (with e being an instance of

MyEnum

) and for the branches, I’m allowed to put something that is not one of the possible values of

MyEnum

(I can put values of other enums). I find this extremely surprising 🙂 Thoughts?

Uzi Landsmann

10/04/2018, 3:04 PM

Hello Kotlin experts! We have a mixed Kotlin/Java project and would like to create data classes defined in Kotlin and use them in our Java code. We like using builders in our code and have used Lombok quite extensively in the past. My question is if there is a way to create automatic builders for Kotlin data classes (like Lombok does for Java classes) to avoid all the boilerplate of writing them by hand. Any suggestions?

Sam

10/04/2018, 4:08 PM

Is there a way to use lambda when dealing with abstract classes? object works but can't use lambda. DialogInterface.OnClickListener is an interface with SAM, BroadcastReceiver is an abstract class with SAM.

private val listener = DialogInterface.OnClickListener { _, _ -> println("interface lambda") }
    private val listener1 = BroadcastReceiver { _, _ -> println("abstract class lambda") } // Error cannot create an instance of abstract class

Hexa

10/04/2018, 7:46 PM

My Intellij is suggesting to add a .

asSquence

before calling

groupBy

on this function that I wrote, but I can't find any evidence to prove if this is a good idea or not. I wonder if anyone here can suggest if this is a good idea. So basically here is what the code look like

//BEFORE adding.asSequence()

                        override fun handle(event: List<String>): Either<Errors.RequestError, Pair<List<Errors.RequestError>, Int>> =
            emailParser.parseEmails(event)
                    .map {
                        Pair(
                                first = it.first,
                                second = it.second
                                        .groupBy { it.emailAdrress }
                                        .map {
                                            Pair(
                                                    first = MessageDestination(it.key),
                                                    second = it.value.map {
                                                        MessageSender(
                                                                message = it.environment
                                                        )
                                                    }
                                            )
                                        }.toMap()
                        )
                    }.flatMap { pair ->
                        service.handleRequests(pair.second)
                                .map {
                                    Pair(pair.first, pair.second.size)
                                }
                    }




 //AFTER adding .asSequence()
   override fun handle(event: List<String>): Either<Errors.RequestError, Pair<List<Errors.RequestError>, Int>> =
            emailParser.parseEmails(event)
                    .map {
                        Pair(
                                first = it.first,
                                second = it.second
                                        .asSequence()
                                        .groupBy { it.emailAdrress }
                                        .map {
                                            Pair(
                                                    first = MessageDestination(it.key),
                                                    second = it.value.map {
                                                        MessageSender(
                                                                message = it.environment
                                                        )
                                                    }
                                            )
                                        }
                                        .toList().toMap()
                        )
                    }.flatMap { pair ->
                        service.handleRequests(pair.second)
                                .map {
                                    Pair(pair.first, pair.second.size)
                                }
                    }

Hullaballoonatic

10/04/2018, 8:27 PM

also can you think of a more succinct way to reference the class of a property than

foo::class

, and

KClass<Bar>

Dominaezzz

10/04/2018, 8:35 PM

Why isn't the compiler happy with

val num: UInt = 5

Sam

10/04/2018, 8:53 PM

Is this style of using apply and run recommended?

IntentFilter().apply {
                addAction( packageName +  INTENT_ACTION_OPEN )
                addAction( packageName +  INTENT_ACTION_CLOSE )
            }.run {
                registerReceiver( receiver, this )
            }

Hullaballoonatic

10/04/2018, 9:16 PM

what are the chances we will be given the ability to add custom operators? i'm guessing low to impossible given the existence of infix

Title

Hullaballoonatic

10/04/2018, 9:16 PM

what are the chances we will be given the ability to add custom operators? i'm guessing low to impossible given the existence of infix

karelpeeters

10/04/2018, 9:17 PM

See scala for how this tends do go wrong.

Hullaballoonatic

10/04/2018, 9:18 PM

is it mostly just a case of misuse? unreadable code?

karelpeeters

10/04/2018, 9:19 PM

Yeah. Here's a classic example: http://www.scala-graph.org/guides/core-initializing.html

Mike

10/04/2018, 9:20 PM

Or look at SBT. Until you know it, the operators feel random.

Hullaballoonatic

10/04/2018, 9:42 PM

do you think kotlin shouldn't employ features that can be used sloppily? i feel like it's a bit late for that with extension functions and properties.

i love kotlin because it can be written as to be supremely readable, and i think custom operators have the potential to improve that aspect, and i'm willing to see any feature capable of that, even if it can be greatly misused to the opposite effect

Mike

10/04/2018, 10:35 PM

Of course not. Great code can be written in any language, just like terrible code can be written in any language. I’m happy with Kotlin’s overloaded limited operators. But yes, any feature, when used well, can improve things. So it comes down to the team…

➕ 1

Hullaballoonatic

10/04/2018, 10:38 PM

honestly, one thing i'm most eager for is the further establishment of Kotlin codestyle, like how best to write chained scope functions, where if/else is appropriate to forego brackets, at what point should a single line property definition be split up, etc

Mike

10/04/2018, 11:24 PM

chained scope style is definitely a biggie. Makes such a difference in reading if it’s the way ‘you’ expect it to be vs when it isn’t. I don’t think the IntelliJ formatter provides quite enough control over formatting of things like that, although I haven’t looked super close. Also, on topic of operators, I’m curious about some examples as it would appear you have some ideas already. I was very glad to see they allowed overriding the arithmetic operators, as there are many cases where being able to do that cleans up code while keeping it feeling ‘natural’.

Hullaballoonatic

10/04/2018, 11:44 PM

One cool example is the

operator in D&D.

1d10+5

. I know infix does that, but I don't like the spaces. We could also create our own mathematical operators like a power operator

**

Mike

10/04/2018, 11:57 PM

Hmmm. I suspect another reason would be the impact on the compiler. Parsing that

out makes parsing take longer. Kotlin is already slower than Java, and a lot of people complain about Scala’s compiler speed. If you use the language, you stop caring, or don’t notice, but when you’re first starting out…

It’s a tough call designing a language. Glad I’m not doing it 😉

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