kotlinlang #announcements

Moreover, Kotlin's concept of suspending function provides a safer and less error-prone abstraction for asynchronous operations than futures and promises. Could someone explain why this is true?

aidan

06/26/2019, 8:34 AM

Is there a profiler for kotlin?

rdgoite

06/26/2019, 3:47 PM

Hello everyone. I’m trying to run my Kotlin Scratch files on Intellij, but it doesn’t give me the option to run it. I came across this issue that’s 4 years old, and seems to have been labeled done. Is this still a known issue? https://youtrack.jetbrains.com/issue/KT-10368

nikolaymetchev

06/26/2019, 6:15 PM

Hello Everyone, Does anyone know if there is a Kotlin DSL that can be used to generate Java code (or even better generate Kotlin Code).

Hullaballoonatic

06/27/2019, 2:21 AM

I've started getting addicted to this format instead of abstract or open classes, and I imagine that's a bad thing:

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interface Foo {
    val foo: Int
    val bar: String?

    companion object {
        operator fun invoke(foo: Int, bar: String? = null) = object : Foo {
            override val foo = foo
            override val bar = bar ?: otherLogic...
            // etc
        }
    }
}

In a lot of ways it's like having the ability to inherit from multiple classes. That's probably not a good freedom to have, though.

invoke

operator has a few advantages over

constructor

, too, such as error checking the arguments prior to instantiating the object. This also opens up delegation to cut down on code You'd think it'd be unfortunate you couldn't do this:

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class Foozle(foo: Int, bar: String?) : Foo(foo, bar)

But you can instead just do this:

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class Foozle(foo: Int, bar: String?) : Foo by Foo(foo, bar)

I'd love to hear the drawbacks to this overall approach

😱 1

Paul Woitaschek

06/27/2019, 8:17 AM

For extension functions. When do you use the prefix

as

and when do you use the prefix

to

bod

06/27/2019, 8:24 AM

Hello, World! I have a strange issue, wondering if it's already known. I have a method with this signature:

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fun foo(vararg pairs: Pair<String, (String) -> FooBar>)

When I call it like this:

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foo(
           "a" to { _ -> FooBar() },
           "b" to { _ -> FooBar() }
      )

I get warning saying that

_ ->

is redundant. But, if I remove it I get

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Type inference failed. Expected type mismatch: inferred type is Pair<String, () -> FooBar> but Pair<String, (String) -> FooBar> was expected

Could this be a problem with the "new type inference algorithm"?

Neil

06/27/2019, 9:16 AM

How does a parent class execute code at the end of construction, after all the subclass' properties have been initialized and their init{} blocks run?

mike_shysh

06/27/2019, 10:52 AM

Hi, if an argument in some function is

Class<T> type

Is it possible to provide List<ObjectA>.class (seems such syntax is not ok in kotlin)?

juliocbcotta

06/27/2019, 1:55 PM

Hi, Would be possible to have a version of this method using generics? So the interface could be

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fun getListener(): MyListenerInterface {
return when {
            parentFragment is MyListenerInterface -> parentFragment as MyListenerInterface
            targetFragment is MyListenerInterface -> targetFragment as MyListenerInterface
            else -> context as MyListenerInterface
        }
}

06/27/2019, 2:07 PM

1.3.40 shipped a

typeOf

intrinsic to create a

KType

but you cannot get a

Type

from that without kotlin-reflect... yet https://youtrack.jetbrains.com/issue/KT-32241

👍 2

06/27/2019, 3:46 PM

is there a thread-safe version of

mutableMapOf()

? i need the map to be thread-safe, and also hold its entries in the order of insertion.

Nicole

06/27/2019, 5:03 PM

Someone did several comparisons with

Float.NaN

which led to this odd result:

Float.NaN === Float.NaN

false

with JVM and JS targets, and

true

with Kotlin/Native. — I see that identity equality for

Float

has been deprecated, but still figured I should check if this is a bug (and should be reported) or if it’s just “undefined behavior”

Hullaballoonatic

06/27/2019, 6:42 PM

Is kotlin now using

for anything? Bitwise operators? Would be kinda neat if

could be a new bracket type if kot, but that would be weirdly different from industry standard.

streetsofboston

06/27/2019, 7:32 PM

In the kotlin playground (play.kotlinlang.org), is there a way to print out an uncaught exception from a Coroutine (when calling

launch

from a scope without a CoroutineExceptionHandler)? Update: Solved

mathew murphy

06/27/2019, 10:22 PM

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launch (newSingleThreadContext("DedicatedThread")) {
    Thread.sleep(1000L)
}

laimiux

06/27/2019, 10:22 PM

Weird question: are there any reason why we can’t do (besides current compiler)

val optional: String? = if (someCondition) { "" }

ValV

06/28/2019, 12:48 PM

How to use

kotlinx.cli

in project (Gradle)? I'm not sure that I'm adding it correctly as a dependency (it is not found). Or I'm missing something else?

haroldadmin

06/28/2019, 4:40 PM

What coroutine scope do you use to launch coroutines in classes that don’t necessarily have a lifecycle? I’m creating a NotificationManager class in an Android application, and I need to use coroutines for taking some database related tasks off the main thread. This class will be used as a singleton in the project via dependency injection. • Should I implement the Coroutine Scope interface in it? There will be no lifecycle callback to cancel the running coroutines in this scope, though • Should I just use GlobalScope if I don’t have a way to cleanup resources anyway?

mathew murphy

06/28/2019, 5:21 PM

Inside a

with (foo)

block, is there any way to indicate that I mean variable

bar

from outside the block, rather than a property

bar

of object

foo

mathew murphy

06/28/2019, 5:57 PM

Is there something that's like a combo of

use

and

with

Timothy Wong

06/28/2019, 7:08 PM

Hi guys, is this some compiler bug? With the code https://hasteb.in/tosejohu.kotlin, the node.left and node.right are not automatically casted as thecorrect types, even though the if statement checks, and we can see from the docs that it technicaly should. https://kotlinlang.org/docs/reference/typecasts.html

var local variables - if the variable is not modified between the check and the usage, is not captured in a lambda that modifies it, and is not a local delegated property;

Luis Munoz

06/28/2019, 7:40 PM

If I have a kotlin class that takes a function as an argument (a block). How do I initialize that class from java, link to documentation might suffice. I don't see that in https://kotlinlang.org/docs/reference/java-interop.html ?

kevinherron

06/28/2019, 7:41 PM

anyone know if it’s expected that some String.format calls don’t work with unsigned types?

Nikolai

06/29/2019, 5:31 AM

Hi, everyone I have simple question, maybe it's already answered somewhere but didn't managed to find answer. In Kotlin documentation about lambda formatting :

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If a call takes a single lambda, it should be passed outside of parentheses whenever possible.

and IDEA always show warning in code about this. I wondering why it should be formatted in that way? Is it just style and readability guidelines? Or it have technical meaning behind it?

Fudge

06/29/2019, 6:30 AM

Is there a way to add a method to an enum class without reflection? If I have

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enum class Test{
foo
}

Then kotlin comes built in with

values(), valueOf()

, but how can I add a new helper method like

getValueNames()

gianluz

06/29/2019, 3:48 PM

Hello everyone!! i have a problem executing a script with dependencies: here my script file:

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@file:Repository("<https://repo1.maven.org/maven2>")
@file:DependsOn("org.apache.commons:commons-text:1.6")

import org.jetbrains.kotlin.script.util.DependsOn
import org.jetbrains.kotlin.script.util.Repository

import org.apache.commons.text.WordUtils

val hello = "helloWorld"
print(hello)
print(WordUtils.capitalize(hello))

then i execute the script:

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kotlinc -cp /usr/local/lib/danger/kotlin-main-kts.jar -script script.main.kts
script.main.kts:7:12: error: unresolved reference: apache
import org.apache.commons.text.WordUtils
           ^
script.main.kts:11:7: error: unresolved reference: WordUtils
print(WordUtils.capitalize(hello))
      ^

basically doesn't resolve the dependencies 😕 and i don't want to link directly the jar when executing the script