kotlinlang #announcements

so when you have an array as a property of a data class, idea recommends you override equals and hashcode, then provides you with an implementation. Is that the same as the default data class implementation? if no, why not? if yes, why would the warning disappear?

jojo.lichtenberger

11/11/2019, 9:09 AM

Hey, I'd love to use Kotlin in a multi-module Open Source maven project. I've used it in one module exclusively. In other modules I'm currently using Java 13. Would you advise on using Kotlin and Java in a single module? I'd love to switch but don't want to rewrite everything. I haven't tried yet, but I guess the IntelliJ Java to Kotlin Converter for classes doesn't produce idiomatic Kotlin code, so I think it's better to just call the Java code from Kotlin and vice versa. Would you advise on mixing Java and Kotlin in a single module? Are there any pitfalls? Or should I have Java and Kotlin modules seperated from each other?

Slackbot

11/11/2019, 10:08 AM

This message was deleted.

Burkhard

11/11/2019, 1:22 PM

How do I enable experimental type inference again. I’m sure I read somewhere that it is possible, but I can’t seem to find any article about it

ghedeon

11/11/2019, 3:47 PM

Is it possible to use

Result<T>

in Java? All extensions seem to be

InlineOnly

, how would you fold this class?

ianrumac

11/11/2019, 4:13 PM

I wanted Unions so I hacked them in via annotations, if anyone needs them: https://github.com/lotuslambda/unikons

👍 2

Ellen Spertus

11/11/2019, 6:35 PM

Normally I prefer

when

switch

, but I created this monstrosity in order to combine multiple

is

cases. Is there a better way without changing the sealed class

ConnectionState

(which I might end up doing)?

if (savedConnectionState is ConnectionState.Isolated) {
    view.initializeButtons(true, false)
} else if (savedConnectionState is ConnectionState.Advertising || 
    savedConnectionState is ConnectionState.Discovering ||
    savedConnectionState is ConnectionState.Initiating ||
    savedConnectionState is ConnectionState.Authenticating ||
    savedConnectionState is ConnectionState.Connecting) {
    view.initializeButtons(false, false)
} else if (savedConnectionState is ConnectionState.ReadyToSend) {
    view.initializeButtons(false, true)
} else if (savedConnectionState is ConnectionState.Failure) {
    view.initializeButtons(false, false)
}

nwh

11/12/2019, 12:17 AM

Are there plans for expanding the current commenting system of Kotlin? For example, being able to reference a specific function by argument type like

See also: [String.toUpperCase(Locale)]

So that overloaded functions can be differentiated?

Animesh Sahu

11/12/2019, 5:53 AM

apply with a suspendable block?

Kate

11/12/2019, 8:15 AM

@Alina Dolgikh [JB] how can I join your Russian kotlin slack workspace?

Mani

11/12/2019, 9:20 AM

casting l1 as ArrayList is working fine

Paul Woitaschek

11/12/2019, 10:28 AM

How can I convert this code to kotlin?

public static JsonAdapter<?> create(Class<?> rawType) {
    return new SafeEnumJsonAdapter<>((Class<? extends Enum>) rawType).nullSafe();
  }

Stephan Schroeder

11/12/2019, 3:27 PM

So i want to deserialize a string into a

Data.Single

but it fails.

sealed class Data<T: Any> {
    class Single<T: Any>(val single: T?): Data<T>()
    class ListOf<T: Any>(val list: List<T>): Data<T>()
}

Could the reason for the mismatch be that the constructor parameter

single

is nullable?? The error message is: com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of
uk.co.whichdigital.pricingengine.Data$Single
(although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value (‘up and running’) Here is my current jsonMapper config:

private val jsonMapper = ObjectMapper().apply {
        registerModule(KotlinModule())
        configure(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES, true)
        configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
    }

UPDATE: I changed the code to `Data.Single`’s generic parameter is nullable

class Single<T>(val single: T): Data<T>()

but the error message didn’t change.

Oleg Siboglov

11/12/2019, 5:02 PM

Could someone please tell me what the Kotlin equivalent of this

<T extends LifecycleOwner & ViewModelStoreOwner>

would be?

Sandeep Gurram

11/13/2019, 7:25 AM

Hi Guys, are scoped function(run, let, apply, also) having anything to do with threads ? are there thread safe ?

Andreas Unterweger

11/13/2019, 10:33 AM

hello all, i have a question regarding mockk kotlin mocking framework. how can i mock all instances of an class? i tried:

val ibMock = mockkClass(InstalledBase::class)
every { ibMock.getModelDescriptions() } returns emptyList<ModelDescription>()

but it doesnt work. getModelDescriptions() still returns another list. i have no access to the object instaledbase in my test, but i want that getModelDescriptions() always returns an empty list

Brian Carbone

11/13/2019, 3:55 PM

get() = field.coerceAtLeast(0)

I don't know how to make a delegate to replace this

louiscad

11/13/2019, 4:32 PM

Hi, I'm looking for your recommendations to parse a simple xml file that doesn't go deeper than 3 levels. Here's an example of the kind of files I'm going to parse: https://dl.google.com/dl/android/maven2/androidx/lifecycle/lifecycle-runtime/maven-metadata.xml In the end, I want to get a list of the available versions. Is there a light library that I should use, or is that overkill and I should just use Kotlin stdlib to do it? Thanks for your input!

Fudge

11/13/2019, 8:14 PM

Were smart casts recently changed to work on mutable variables??!

Ky Leggiero

11/13/2019, 10:54 PM

I wish I could hate this 😂

👌 1

🤣 6

😂 28

😅 6

Tauhid Rehman

11/14/2019, 2:26 AM

does anyone know if kotlin has a built in library that uses the

.mask

function? basically I need to mask a certain number of integers with a

ursus

11/14/2019, 5:06 AM

Hi, I want to ask about local functions. Is there any penalty to calling a function which defines a local function inside it? Does it get "redefined" every call or is there something clever in the compiler?

Mohamed Ibrahim

11/14/2019, 7:03 AM

how to use kotlin sealed classes in java/Rxjava

Cyberpunk Keanu

11/14/2019, 4:21 PM

Hey all, I'm new here. With my recent discovery of Ktor as an Android Developer working in Kotlin, I'm more intrigued about building my own Kotlin Written Server Backends without having to rely much on my team's backend developers. However, almost no one here writes server backend in Kotlin. Everyone's on Node.js & Express.js, saying Ktor doesn't have a Future Scope. So asking you guys, can Ktor grow into something which can be use to write Production level Server Backends?

Ben Madore

11/14/2019, 9:09 PM

anyone else using spotless gradle plugin with ktlint? and finding that it doesn’t seem to actually check the same things at ktlint? i.e. if i run

gradle spotlessCheck

i get no issues, but i get a lot when i run

ktlint

eekboom

11/14/2019, 10:13 PM

I assume that

tasks.compileKotlin {
	kotlinOptions.jvmTarget = "1.8"
}

is the same as

tasks.compileKotlin.configure {
	kotlinOptions.jvmTarget = "1.8"
}

Can somebody explain to me how this magic works?

compileKotlin

is a property of type

TaskProvider<org.jetbrains.kotlin.gradle.tasks.KotlinCompile>

which is an interface with two abstract methods, so it can't be SAM, right?

eekboom

11/14/2019, 10:18 PM

Ok, it seems that rubber ducking works even when just talking into the void 😉 I found this in `NamedDomainObjectProviderExtensions`:

operator fun <T> NamedDomainObjectProvider<T>.invoke(action: T.() -> Unit) =
    configure(action)

Nice.

Akhil Sunny

11/14/2019, 11:00 PM

Hey All , I am trying to write tests for a Kotlin MPP - for iOS testing found using a simulator - https://github.com/JetBrains/kotlin-native/issues/2426 -

task iosTest {
    def device = project.findProperty("iosDevice")?.toString() ?: "iPhone 8"
    dependsOn 'linkTestDebugExecutableIos'
    group = JavaBasePlugin.VERIFICATION_GROUP
    description = "Runs tests for target 'ios' on an iOS simulator"

    doLast {
        def binary = kotlin.targets.ios.compilations.test.getBinary('EXECUTABLE', 'DEBUG')
        def infoPlistSrc = file("$rootProject.projectDir/src/iosTest/resources/Info.plist")
        def infoPlistDest = file("$binary.parentFile/Info.plist")

        Files.copy(infoPlistSrc.toPath(), infoPlistDest.toPath(), StandardCopyOption.REPLACE_EXISTING)

        exec {
            commandLine 'export', 'SIMCTL_CHILD_CFNETWORK_DIAGNOSTICS=3'
            commandLine 'xcrun', 'simctl', 'spawn', device, binary.absolutePath
        }
    }
}

- this simulator runs in a terminal and executes the tests. But I can't find any reports generated by it(html/xml ). Is it possible to have reports generated by this simulator ? or is there any other way to generate reports while unit testing a Kotlin iOS output ? . Pls help

bodiam

11/14/2019, 11:23 PM

Is there any ETA on Kotlin 1.3.60 ?

james

11/14/2019, 11:45 PM

I'm wondering if someone can show me the Kotlin-idiomatic way to solve the following. I have a list of objects which gets returned from a repo and I'd like to transform them into another object, while throwing away objects that are deemed "invalid".. where invalid in this example is if

it.nullableField

is null. I've tried the following, but it doesn't work as expected because the smart cast fails, as seen in comment:

repo.getThings()
    .mapNotNull {
        if (it.nullableField != null) {
            SomeOtherThing(
                id = it.id,
                name = it.name,
                requiredField = it.nullableField // compiler error: Smart cast to String is impossible because it.nullableField is a public API property declared in a different module
            )
        } else null
    }

Title

james

11/14/2019, 11:45 PM

it.nullableField

is null. I've tried the following, but it doesn't work as expected because the smart cast fails, as seen in comment:

repo.getThings()
    .mapNotNull {
        if (it.nullableField != null) {
            SomeOtherThing(
                id = it.id,
                name = it.name,
                requiredField = it.nullableField // compiler error: Smart cast to String is impossible because it.nullableField is a public API property declared in a different module
            )
        } else null
    }

streetsofboston

11/14/2019, 11:48 PM

Insert a

.filter { it.nullableField != null }

into the chain. Then just do

.map { SomeOtherThing( ..., ..., requiredField = it.nullableField!!) }

You still would need the

!!

check; smart-casting won’t work in this case

james

11/14/2019, 11:49 PM

I considered that, and I considered just adding !! to

it.nullableField

where my comment is. both of these seem to work, but I'm wondering what the idiomatic way is?

using

filter

feels more readable at least

basher

11/14/2019, 11:51 PM

repo.getThings()
    .mapNotNull { thing ->
        thing.nullableField?.let {
            SomeOtherThing(
                id = thing.id,
                name = thing.name,
                requiredField = it
            )
        }
    }

james

11/14/2019, 11:58 PM

I considered that too, Ben, but my main concern there is that it limits me to a single field being checked.

I'm leaning towards using

filter

anyone have any other ways of achieving it?

basher

11/14/2019, 11:58 PM

oh i see 👍

Matteo Mirk

11/19/2019, 12:29 PM

I think

filter

is the best option

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