kotlinlang #announcements

Given a java class with a setter taking a non-nullable value, and kotlin extension function with a nullable parameter, what's idiomatic way to call the setter if the param is non-null?

fun MyPojo.init(fieldName: String? = null) {
            fieldName?.let(::setFieldName)
            fieldName?.also { setFieldName(it) }
            fieldName?.also { this.fieldName = it }
            if(fieldName != null) setFieldName(fieldName)
            if(fieldName != null) this.fieldName = fieldName
}

dmcg

12/14/2018, 1:37 PM

Anyone got a good way of making a parent-child relationship without mutating one or the other? https://stackoverflow.com/questions/53130288/how-do-i-create-a-parent-child-relationship-in-immutable-kotlin-classes

xenoterracide

12/14/2018, 6:54 PM

dependencies {
    compile(kotlin("stdlib", "1.3.11"))
}

w: Runtime JAR files in the classpath have the version 1.2, which is older than the API version 1.3. Consider using the runtime of version 1.3, or pass '-api-version 1.2' explicitly to restrict the available APIs to the runtime of version 1.2. You can also pass '-language-version 1.2' instead, which will restrict not only the APIs to the specified version, but also the language features
w: /tmp/.gradle-test-kit-xeno/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib-common/1.2.71/ba18ca1aa0e40eb6f1865b324af2f4cbb691c1ec/kotlin-stdlib-common-1.2.71.jar: Runtime JAR file has version 1.2 which is older than required for API version 1.3
w: /tmp/.gradle-test-kit-xeno/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib/1.2.71/d9717625bb3c731561251f8dd2c67a1011d6764c/kotlin-stdlib-1.2.71.jar: Runtime JAR file has version 1.2 which is older than required for API version 1.3
e: /tmp/junit14078856699846774951/junit17290987759747338376/src/main/kotlin/com/xenoterracide/test/Test.kts: (17, 1): Cannot access script base class 'kotlin.script.templates.standard.ScriptTemplateWithArgs'. Check your module classpath for missing or conflicting dependencies

how do I make kotlin 1.3 work? or heck, even 1.2… no matter what I seem to do it seems to end up with this error

Dico

12/14/2018, 8:15 PM

Are the messages from @xenoterracide And @blogscot related?

tschuchort

12/14/2018, 10:59 PM

Is there any way to pass

this

to a mixin class that implements an interface via delegation? (i.e.

class Class : Interface by Mixin(this)

. It's possible to pass

this

but for some reason it refers to the companion instead of the instance itself. I realize that I could just instantiate the mixin in the class body and delegate all methods manually, but that's quite annoying.

Dalinar

12/15/2018, 8:22 AM

I'm using a java library called Caffeine which is actually fairly similar to Guava Caches in syntax. However, I've run into this problem (I'm extremely rusty on Kotlin since I haven't touched it in a year).. so.. how do I solve this? (make it nicer)

`
private val requests: Cache<String, Req> = Caffeine.newBuilder()
            .removalListener<String, Req> { clientOrderID: String?, req: Req?, removalCause: RemovalCause ->
                clientOrderID!!; req!!
                ...
                req.close()
            }
`

with Guava the code would compile without the `?

on the parameters

the reason I added these

where I did was because I refer to these variables several times in the code afterwards. However what I'm asking is if there is a nicer syntax where I can somehow get rid of the

?` on the parameters very strange, my other similar caches built in the same way have no problem accepting non-nullable parameters in
removalListener
- it's just this particular one that is the problem

xenoterracide

12/15/2018, 8:44 AM

does kotlin have a BOM for its "core" libraries?

xenoterracide

12/15/2018, 6:05 PM

the getter is required by Persistable

xenoterracide

12/15/2018, 6:06 PM

are there any issues to vote for regarding private/protected vals on interfaces?

simon.vergauwen

12/16/2018, 12:26 PM

Any1 has experience with CircleCI? My builds keep failing with exitcode 127. According to CircleCI docs that means that my mem consumption is too high and they’re killing the gradlew child process.

Dominaezzz

12/16/2018, 4:30 PM

If a member function only uses public members of it's class, should it be converted to an extension function? :yes:/🇳🇴

itnoles

12/16/2018, 6:19 PM

Travis CI has flaky network connections

aris

12/16/2018, 7:50 PM

i have a error because after $ i have a qh41, and kotlin think is a variable

Paul Woitaschek

12/16/2018, 9:21 PM

It's my own project, the modules are my modules, what's impossible here for a smartcast?

groostav

12/17/2018, 1:52 AM

can somebody tell me why this is legal kotlin?

-.groovy

:youtrack: 1

🐞 1

Czar

12/17/2018, 1:12 PM

Are we stuck with the following situation? java declaration

public abstract <R> java.util.concurrent.CompletableFuture<R> send(Object command)

Java call

object.send(command);

nice 👍 :java: Kotlin call

object.send<Any>(command)

not nice, I'd like to avoid having to write

<Any>

👎 :kotlin:

Paul Woitaschek

12/17/2018, 1:52 PM

I like it because for me a class like this is actually rather a function than a class with actual methods. So this ready naturally.

Slackbot

12/17/2018, 8:08 PM

This message was deleted.

serebit

12/18/2018, 12:15 AM

So when are we getting kotlin.color/kotlinx.color?

❓ 9

Amir

12/18/2018, 8:35 AM

Hey guys, I'm new to programing and I decided to learn Kotlin and I'm more interested in Kotlin for Android. Is there any website with tutorials for complete beginners? Also, is it better to first start with learning Kotlin itself and then learn kotlin for Android, or I can learn from very beginning the kotlin for Android.

karelpeeters

12/18/2018, 8:41 AM

Do you already know Java? If so, I'd recommend going trough the reference starting here: https://kotlinlang.org/docs/reference/basic-syntax.html and after that start Android.

rrader

12/18/2018, 10:52 AM

What library do you use for SQL/Database?

mikehearn

12/18/2018, 2:35 PM

We're going to write a tool to provide ABI stability when new parameters with default values are added, to unblock our release, but it'd be good to know what this param is for - if anything.

grahamborland

12/18/2018, 3:34 PM

Why does this compile?

private fun shouldNotCompile(optionalString: String?): Boolean {
        optionalString?.let {
            return true
        }
    }

I’ve completely forgotten to specify a return value for the case where the

let

is not entered.

🐛 1

grahamborland

12/18/2018, 3:40 PM

Thanks, will report

cristiangm

12/18/2018, 5:12 PM

Kotlin compiler prints warnings but, it would be wonderful if we could have them on a XML report

SrSouza

12/18/2018, 6:20 PM

Have one more question, everytime a create and use a function with contract I need to add the annotation

@ExperimentalContracts

Rohan Maity

12/18/2018, 10:52 PM

@elizarov is there any chance that jetBrains come for GSOC'19 for Kotlin Lang ?

tipsy

12/19/2018, 9:29 AM

i'm trying to call a jdbi-method from kotlin, and i get:

Type inference failed: Not enough information to infer parameter X in 
fun <R : Any!, X : Exception!> withHandle(callback: ((handle: Handle!) → R!)!): R!
Please specify it explicitly.

the method signature is

public <R, X extends Exception> R withHandle(HandleCallback<R, X> callback) throws X {

what am i supposed to do in this case?

rrader

12/19/2018, 10:23 AM

What Kotlin feature is used for

object Users : Table() {
    val id = varchar("id", 10).primaryKey() // Column<String>
    val name = varchar("name", length = 50) // Column<String>
    val cityId = (integer("city_id") references Cities.id).nullable() // Column<Int?>
}
Users.insert {
            it[id] = "andrey"
            it[name] = "Andrey"
            it[cityId] = saintPetersburgId
        }

how compiler know that

it[id]

is valid and for example

it[title]

is not valid? from https://github.com/JetBrains/Exposed

Title

rrader

12/19/2018, 10:23 AM

What Kotlin feature is used for

object Users : Table() {
    val id = varchar("id", 10).primaryKey() // Column<String>
    val name = varchar("name", length = 50) // Column<String>
    val cityId = (integer("city_id") references Cities.id).nullable() // Column<Int?>
}
Users.insert {
            it[id] = "andrey"
            it[name] = "Andrey"
            it[cityId] = saintPetersburgId
        }

how compiler know that

it[id]

is valid and for example

it[title]

is not valid? from https://github.com/JetBrains/Exposed

reik.schatz

12/19/2018, 11:00 AM

maybe ask in #exposed but it looks like

.insert

is an extension function and then

id

name

and

cityId

are just

Column

instances given to the

InsertStatement

and

val title: Column<?>

just doesn’t exists in your

Users

object

rrader

12/19/2018, 11:03 AM

but how it knows that columns are from

Users

and not from other

object

reik.schatz

12/19/2018, 11:06 AM

because

.insert

is added to

Users

fun <T:Table> T.insert(body: T.(InsertStatement<Number>)->Unit): InsertStatement<Number> = InsertStatement<Number>(this).apply {
    body(this)
    execute(TransactionManager.current())
}

is a specific type

again, I am new to Kotlin. ask in #exposed 🙂

rrader

12/19/2018, 11:45 AM

ok, thanks

Mike

12/19/2018, 1:48 PM

@rrader

insert

is an extension function on all types.

body

is a Lambda with receiver. Some more advanced Kotlin features that allow for powerful DSL’s. Hopefully those keywords give you some direction for research. But ultimately, the Lambda you’re passing to

insert

(everything inside the {}) has a single parameter

it

that is of the type of the class

insert

is being called on. So in this case, the compiler knows that

it

is of type

Users

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