kotlinlang #announcements

interface SwitchMessageConverterKotlin<T>  {
    val supportedType: Class<T>
        get() = supportedKlass.java

    val supportedKlass: KClass<T> // Anyone know why the compiler complains about this `T`?
}

kirillrakhman

10/04/2017, 7:56 AM

Interesting

class Foo: (key: String) -> String

gives an error "Unsupported: named parameter in function type in supertype position", but

typealias KeyFunction = (key: String) -> String
class Foo: KeyFunction

actually works. The benefit is that when you let IDEA generate the missing members, the parameter name is set to

key

instead

p1

🤔 1

Olekss

10/04/2017, 9:11 AM

in reality what would I need is some sort of pattern matching DSL across given JSON

s.luhmirins

10/04/2017, 11:40 AM

is there a function in std-lib for cases like this?

.let {
    when (it) {
        // ...
    }
}

myanmarking

10/04/2017, 12:33 PM

guys i need an advice, i know its not kotlin specific but maybe some1 can help. Is there any way to wrap a retrofit error response into an exception?. The errors response json is like this:

{
  "code": "K_PRO_BE_ERR_REGIST_INVAL_USER_AGE",
  "message": "Age requirement was not respected."
}

:stackoverflow: 4

rwachol

10/04/2017, 1:23 PM

so I will ask something kotlin related 😉 Will kotlin support java9 runtimes? meaning, will I be able to create very minimal javafx kotlin app ?

10/04/2017, 4:46 PM

anyone here using Kotlin for web development on a regular basis? I'm really interested in using it in this space, but curious what others are using as the platform (outside of Kotlin itself)

karelpeeters

10/05/2017, 5:39 AM

Just like in Java, you syncronize on the value,

true

false

, not on the variable. For this reason it's a really bad idea to ever use a primitive for synchronization.

lovis

10/05/2017, 8:56 AM

wasn’t there a keep/issue to support

it

inside

when

? what’s the status? i can’t find it 🤔

Fré Dumazy

10/05/2017, 10:24 AM

Hi, I was wondering, is there something shorter for

CharSequence.takeIf { it.isNotBlank() }?.let { doSomethingWithThis(it) }

to execute code only if a String or CharSequence is not null or blank?

10/05/2017, 11:21 AM

Is there anything in the stdlib that allows zipping two collections together, but padding the result with nulls if one collection is shorter? Kind of like

fun <T, R> Iterable<T>.zipPadded(other: Iterable<R>): List<Pair<T?,R?>>

Czar

10/05/2017, 11:26 AM

I have a feature proposal, want to hear some feedback before posting to YT: Let's say we have this interface:

fun <E : Entity, ID : Serializable> getRequired(id: ID): E

We can use it either like a)

getRequired<SomeEntity,Long>(1L)

or b)

val entity: SomeEntity = getRequired(1L),

It seems to me that case a) is unnecessarily verbose, I'd like to write

getRequired<SomeEntity>(1L)

, because

1L

already contains information about type of the second generic parameter, so compiler can infer it, like it does in case b).

jschneider

10/05/2017, 12:12 PM

`` @Symbol( AM.SYMBOL ) @Definition( {"optical path length through Earth's atmosphere", "relative to path length to that at the zenith at sea level"} ) public @interface AM { String SYMBOL = "AM"; } ``

jschneider

10/05/2017, 12:27 PM

That is a little bit disappointing. I hoped that I can do everything with Kotlin that is possible with Java. I try to convert my Java code to Kotlin. But at some points that is not possible without breaking backwards compatibility 😞

joao.alves

10/05/2017, 1:38 PM

Hello everyone. Is there anyone interested in Droidcon London tickets? Droidcon is happening on October 26-27th 2017. Since my company is sponsoring the event we have some extra tickets, so we have 3 personal tickets we don’t need anymore and we would like to give them away for the price we purchased them. The price is £250 each. They’re selling for £774 on the website now and will be an extra £50 after the 13th.

pablisco

10/05/2017, 7:35 PM

I'm trying to find information about how to use Kotlin annotations in Java. But I can't find the right search. Are they fully compatible?

karelpeeters

10/06/2017, 5:56 AM

The kotlin compiler detects annotations and assumes the corresponding nullability @qwert_ukg.

Fré Dumazy

10/06/2017, 8:10 AM

Hi, I'm having some problems with generics: How do I create a method that accepts

<T: MyObject> myMethod(arg: MyWrapper<T>)

and

<T: MyObject> myMethod(arg: MyWrapper<Array<T>>)

If I try this in 2 methods with the same name, it says "The following declarations have the same JVM signature"

marstran

10/06/2017, 11:45 AM

I would make immutable data classes, and use copy:

val newObj = obj1.copy(name = obj2.name, ....)

👍 3

jcogilvie

10/06/2017, 4:05 PM

fair point. basically this is ported from a java String.format() call, which is more efficient than string literal concats iirc, so I guess I'm still trying to avoid the latter. not sure if kt improves java in that regard?

orangy

10/06/2017, 8:42 PM

We have #rant in our JetBrains’ internal Slack 🙂

👍 1

ayrat555

10/07/2017, 9:00 AM

Are coroutines replacement for java 8's completable future?

geekasm

10/07/2017, 9:56 AM

open class dmap( val map : Map< String, Any > )

inline fun <T : dmap, reified TValue : dmap> T.dmap(): ReadOnlyProperty<T, TValue> {
    return object : ReadOnlyProperty<T, TValue> {
        override fun getValue(thisRef: T, property: KProperty<*>) = TValue( thisRef.map[property.name] ) )
    }
}

christophsturm

10/08/2017, 9:07 AM

must be a very powerful lib if you are using it despite its api

Shawn

10/09/2017, 3:24 PM

Nobody is arguing against using early returns at all. What we are a bit concerned about is the fact that this code snippet is pretty hard to interpret, and that in of itself may warrant rewriting this block to be more easily understood. That said, sure, in a vacuum “style” does not solve your problem, but it does make it harder to give you advice. Based on your initial snippet, I would suggest something that looks more like this:

when (i) {
  in 0..10 -> println("matched")
  else -> println("not matched")
}
println("finished")

10/10/2017, 4:17 AM

.map(::MyClass)

Paul Woitaschek

10/10/2017, 8:41 AM

@Kulwinder Singh Please don't crosspost

edwardwongtl

10/10/2017, 9:40 AM

Can you post some of the

build.gradle

code up here?

gildor

10/10/2017, 9:41 AM

Is that just IDE message or you have problems with build or code highlighting?