kotlinlang #announcements

Hi, id like to ask, copy ctor from data classes, with default parameters used to only change one thing while keeping others .. how would one translate it to java?

ribesg

03/01/2018, 7:42 AM

Is there still no way to reload a file from disk in a run configuration in IntelliJ?

hhariri

03/01/2018, 12:21 PM

KotlinConf Super Early Bird and Workshop Tickets are now available. Heads-up that the number of tickets at this price are limited (as are the seats at the workshops) https://twitter.com/kotlinconf/status/969183192551960578

:kotlin: 11

💯 2

👏 4

Arun

03/01/2018, 2:36 PM

Is there a good example on how to use

buildString()

? https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.text/build-string.html

locke

03/01/2018, 3:57 PM

Didn't know if there was a more comprehensive one.

Joakim Fast

03/01/2018, 4:33 PM

Yes it is

Shawn

03/01/2018, 5:44 PM

surprised

@kotlin

hasn’t posted that yet

brabo-hi

03/01/2018, 5:49 PM

i love kotlin, i really really love kotlin...just started working on it since couple time, and it changed my life 🙂. I come from Java/Scala 😫 @. I have question. How do we deal with static variable in kotlin ?

poohbar

03/01/2018, 6:46 PM

fun `hi hello`()

The name of the function now has a suggestion on it: "Remove redundant back ticks". They are not redundant and the action does nothing. Could anyone confirm?

:youtrack: 1

tschuchort

03/01/2018, 7:01 PM

is there any way to get the default value of a parameter during annotation processing?

vlad

03/01/2018, 9:30 PM

is there some way to deal with the fact that kotlin methods can throw exceptions such as IOException that are “checked” exceptions in java without `throws`in teh signature?

jtravis

03/01/2018, 11:15 PM

I would like to use

when

exhaustively when looking through some sealed classes, but there is no real result from each of the

when

clauses. The best I can currently do appears to be below:

val someVariableThatDoesntDoAnything = when(some) {
        is FirstClass -> {} 
        is SecondClass -> {}
    }

It seems like it would be nice to allow

val _ = when(some) { ... }

jermainedilao

03/02/2018, 3:13 AM

Hi! I’m trying to create a project following Clean Architechture. I’m already done setting up different modules. Including the “domain” module which is a pure java module (to make sure there’s no android components that will be used here). However during build time, It could not resolve the classes inside my “domain” module. What could be wrong here? here’s my dependencies inside my app build.gradle

sindrenm

03/02/2018, 12:50 PM

(That is, what's the difference between

as? String

and

as String?

? 😒imple_smile:)

Andreas Sinz

03/02/2018, 2:32 PM

@Guillaume Imbert possibly something is cached. have you tried a full rebuild? if that doesnt help, maybe try to invalidate the cache of intellij

➕ 1

orangy

03/02/2018, 4:42 PM

We might need some minimal working (non-working) example to suggest anything

ylemoigne

03/02/2018, 6:33 PM

I have a java class

Foo

out of my control which has a method named

div(Bar bar)

; Kotlin seems to allow the usage of this method as an

operator

. But this method, is not really what you can expect for a division. And I would like to implement the

operator fun Foo.div(bar:Bar)=division(bar)

to get the right action.... But as

div

exist, the extension is shadowed. I suppose I'm completely out of luck ? (No way to tell kotlin that the

div()

method in the class is not an operator method ?)

patapon

03/03/2018, 12:02 PM

there is an interface called 'LocalRedeclarationChecker' that may be responsible for that, but I can't figure out where it is called for class members

ylemoigne

03/03/2018, 5:02 PM

It's strange to have to disable an inspection in idea to respect kotlin-coding-convention.... (

Package name does not match containing directory

In pure Kotlin projects, the recommended directory structure is to follow the package structure with the common root package omitted

). And is there a way to give IntelliJ the "base" package for new files under root ?

tipsy

03/03/2018, 8:12 PM

by lazy

supposed to work when calling from java?

ylemoigne

03/03/2018, 8:15 PM

Is there a list of forbidden characters in back-ticked method names ? (And if there is way to circumvent them, as I would like to put a

in it)

liz3

03/04/2018, 1:47 AM

Can someone quickly help me? How exactly does the code looks for the kotlin class to act as a Controller for a JavaFX scene created by a .fxml file? Because in java you leave the variables undefined which will later be referred to the gui object by the fxml loader, now of course i cant leave the var undefined in kotlin. Java:

@FXML
    private ListView<String> entriesList;
    @FXML
    private TextField hostField;
    @FXML
    private TextField nameField;
    @FXML
    private PasswordField passField;
    @FXML
    private TextField pathField;
    @FXML
    private Button testConnBtn;
    @FXML
    private Button saveBtn;
    @FXML
    private Button delBtn;
    @FXML
    private Button saveNewBtn;
    @FXML
    private TextField customPath;
    @FXML
    private ComboBox<String> typeBox;

cedric

03/04/2018, 4:31 AM

@Ruckus @orangy I'd phrase it this way:

lateinit

is very useful when your objects are being managed by a container, and containers typically separate object instantiation from object initializations. Some example containers would be Android, the servlet spec, and probably many others. Technically,

lateinit

has nothing to do with Java and nothing to do with dependency injection.

karelpeeters

03/04/2018, 3:23 PM

more values are of type
Any
compared to
String

But less values are of type

(Any) -> Unit

then of

(String) -> Unit

, so the former is more specific.

CodeIsmail

03/04/2018, 8:41 PM

I'm trying to learn Kotlin using the kotlin-koan and I'm already disappointed with the process. So after cloning the repo, I get errors when running the test. I came across a possible solution stating to run :testClasses gradle task, After doing doing that, every test seem to be passing without solving any exercise. I'd appreciate guidance to setting it up.

jcminarro

03/04/2018, 9:18 PM

Hello, I have had confusion with

when

expresion and I would like to share with you and see what you think about it. I have created a repo that reproduces the problem that I had, you can check here: https://github.com/JcMinarro/SealedClass The problem was with some Sealed Class that has some

object class

. The IDE, when autocomplete the remaining branches, if some of the cases is an

object class

doesn't add the

is

operator at the beginning. I though that the operator

is

was redundant when it was used inside of

when

with an

object class

but It is not the same. I had the problem when I serialized/deserialized that

object class

and I could see that I got a

kotlin.NoWhenBranchMatchedException

Title

jcminarro

03/04/2018, 9:18 PM

Hello, I have had confusion with

when

object class

. The IDE, when autocomplete the remaining branches, if some of the cases is an

object class

doesn't add the

is

operator at the beginning. I though that the operator

is

was redundant when it was used inside of

when

with an

object class

but It is not the same. I had the problem when I serialized/deserialized that

object class

and I could see that I got a

kotlin.NoWhenBranchMatchedException

Andreas Sinz

03/04/2018, 9:35 PM

is

compares the types, without

is

it checks whether its the same runtime-instance. if you serialize/deserialize an

object

, it is a new runtime instance

there was a youtrack issue somewhere about that

for now always use

is

when working with a

sealed class

jcminarro

03/04/2018, 9:37 PM

Yes, I know (Now). Without

is

it compare the value. I would like that IDE suggest you to use always

is

when you work with a

sealed class

Do you know where I could find the youtrack issue that you talk about?

Andreas Sinz

03/04/2018, 9:39 PM

https://youtrack.jetbrains.com/issue/KT-21570

👍 2

raulraja

03/04/2018, 10:03 PM

@Andreas Sinz regardless of the serialization issue, Is this related to Kotlin treating identifiers for the singleton type the same as the value it holds? In Scala there is a

MySingleton.type

explicit synthetic type to be able to refer to the types of singleton objects but in Kotlin we have ambiguity:

when (a) {
  is B -> // type comparison works for class an object
}
when (a) {
  B -> //ambiguos comparison equals based comparison takes precedence
}

Both case would compile fine but in the second one the semantics of the program change since when defaults matches to equals comparison.

in that program if

is a class it would be compared by type but if it's an object it would be compared against the object value and not the object type.

Andreas Sinz

03/05/2018, 8:40 AM

@raulraja yes, your second example is just a

a.equals(B)

where

is the "only" instance of

object B

your second example doesn't work if

is a class. You either need to use

is B ->

to compare the types or

B() ->

to compare with

equals

raulraja

03/05/2018, 10:36 AM

is that the case? It does compile and run but the semantics are wrong because

B ->

is valid for classes. If

was a class it would do a type comparison but if it's an object uses equals based comparison. You can see in @jcminarro repo how the test fails even compiling fine. If you add

is B ->

then it performs the right comparison. This is going to be confusing as it stands in Kotlin to many users and has the potnetial to introduce runtime woas and bugs because of ambiguity. Refactoring the class to an object is common and

when

cases left behind will still compile but yield a different behavior at runtime.

Andreas Sinz

03/05/2018, 11:07 AM

using

class B

B ->

does not compile here with the message:

Classifier 'B' does not have a companion object, and thus must be initialized here

. In his repo he has

SomeSealedClass.SomeObjectClass -> false

which is an object and

is SomeSealedClass.SomeDataClass -> true

which is a data class. I can't find any occurence of

SomeDataClass ->

without

is

in his tests

raulraja

03/05/2018, 11:40 AM

@Andreas Sinz my bad, the IDE fooled me.

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