How to use function overload for list of data type? e.g:

fun fun1(list: List<DataA>)

fun fun1(list: List<DataB>)

The current condition declaration was clashed. any workaround? 1. I've tried to use

typealiases

but it still clashed. e.g: typealias ListDataA = List<DataA> 2. Using extensions function, still clashed. e.g: ListDataA.fun1()

when

doesn't have a short form for

!=

right?

How to use the method option

Int

optional parameter?

Is it good way to define constants as a top level declaration with

internal

key word eg

internal const NAME_FOO:String = " "
class Foo{
}

Is there is specific reason that

<

etc are not supported in

when

(I mean in the same way as

in

and

is

)

Can I use any data type in a

when

statement?

i’ve tried to set up a sealed class that extends an interface in order to get compile-time exhaustiveness, but it doesn’t work the way i wanted it to.

interface ErrorField
data class InputError(
    val field: ErrorField
    val message: String
)

// elsewhere
internal sealed class Field : ErrorField {
    object MyField : Field()
}

// complains about exhaustiveness
return when (error.field) {
    is Field.MyField -> {}
}

is there a way to get the behavior i’m looking for? that is, to have a generally defined type but have the exhaustiveness check be aware that the subtype is actually exhausted?

When I have

when

without an argument and I want to put 2 cases into 1 branch I have to divide them with || , right?

is there a way to design a generic contract that will be implemented using internal types? i.e:

interface Entity
internal class MyClassEntity : Entity {}

interface Model
class MyClass {} : Model

interface Repository<M: Model, E: Entity> {
    fun constructEntity(model: M): E
}

basically I want to expose

MyClass

and implementations of

Repository

, but I want some way to construct entities internally and still have them be part of a contract

I often see people write that

when

without an argument is a replacement for an

if-else-if

ladder. But why particularly the argument-less one? Isn't it also a replacement for

if-else-if

when it has an argument?

having else with return false everywhere is ugly

fun Foo(x: Float?): Boolean {
    var result = false
    if (x != null) {
        result = x > 1f
    }
    return result
}

can this be simplified? maybe using elvis operator somehow?

Hi guys, is there documentation about the higher order functions in collections that show the complexity like O(1) / O(n) etc.?

I have this inline reified function, is there a way for compiler to optimize away when branches other than the matching one (considering it's inline)

suspend inline fun <reified T> get(key: String): T? =
        dao.getById(key)?.let {
            when (T::class) {
                String::class -> it.value as T
                Int::class -> it.value.toInt() as T
                Float::class -> it.value.toFloat() as T
                Double::class -> it.value.toDouble() as T
                else -> throw IllegalArgumentException("Not implemented for the given type.")
            }
        }

data class User(val name: String, val email: String)

val user: User get() = User(email = getEmail(), name = getName())

What is the order of execution here? Do named arguments get resolved (1) according to the data class argument positioning or (2) when creating the object with named arguments?

Is there a standard interface for "class which implements toString()"? Like

Stringer

in Go?

Yes. I guess I'll have to define some other interface, or else Any will be acceptable.

Or its methods

Hello all. Looking to learn a little bit of Kotlin for Android. No serious Java experience outside of some Java for idiots type stuff back in the Java 6 days (or around then). I do have some programming experience in C and C++ (with Qt), Python and Swift but only hobby stuff tbh. Just wondering where the “best” place to start for someone like me is? Not a total newb to programming but not a professional by any means. Books, courses, videos, etc. I am on a Mac (Mojave) if that matters. Thanks!

Could someone explain to me what the deal is with JDK versions? 11 is the latest but 8 seems to be mostly used. One is going to be managed by OpenJDK and the other by OracleJDK? Are there licensing differences as well? Should 8 be used when starting fresh?

What's the difference between mavenCentral and jCenter?

I’m looking for a Kotlin console or REPL (similar to the Groovy console) i.e. - a GUI that allows you to type multiple statements - when the statements are executed, the result of the last expression (or an error) is shown Does such a thing exist? I have the ultimate edition of IntelliJ if there’s a plugin that provides this functionality.

Hi guys, so I have a question regarding lambdas: I have a function like:

fun addVisibilityListener(listener: (Int) -> Unit = {})

I want to create a list of listeners, It is possible to have a list of lambdas? or how can I handle that scenario?

can anyone think of an elegant way of getting the tag-name of a html-tag? currently i have

"<my-tag>...</my-tag>".removePrefix("<").takeWhile { it != '>' }

Hi guys, I've a question: I want to convert a string(say, origin_source = sources) to mutableMap. How to implement with

associateTo

?

What's the best way to use a java class, but make it NonNullable? Wrap it in an inline class? Or is there an easier way? I basically would like to have a kotlin equivalent to a java class (which I can't change)

#getting-started I'm new to Kotlin. Just finished Coursera course on Kotlin and looking for the next steps to learn. Are there good books or resources showing how to use Kotlin for Android development and for Android game development? I saw "Kotlin In Action" that is authored by the instructors of the Coursera course. BUT, it doesn't mention Kotlin development for Android and it's a bit old (aside: is a new edition about to come out?). My day job is desktop C# apps. I did some Android development >5 years ago in JAVA but it's a distant memory. Thanks!

I'm trying to create some sort of compute graph and I'm trying to make my nodes a sealed class to exhaustively match on them with

when

. So I have something like (class internals omitted)

sealed class Node
sealed class SourceNode : Node() // No parents
sealed class SinkNode : Node() // No children
sealed class OpNode : Node()
// classes that extend the sealed classes here

I would like to distinguish at the type level nodes that have parents and nodes that have children so I could write something like:

fun foo(x: ParentNode): ParentNode {
    // Do something to only parent nodes, possibly exhaustively match on them, and return a ParentNode
}

Where

ParentNode

is somehow a subtype of

Node

The problem is

OpNode

is both a parent node and a child node which calls for multiple inheritance via interfaces, but I would like to be within the land of sealed classes for exhaustive matching. Is there a solution to this in kotlin?

If I have classes that implement interface

Foo

, when making a

List<Foo>

should be possible without casting the classes to their interface type? When I do

fun listOfFoos(): List<Foo> {
    return listOf(
        FooA(),
        FooB(),
        FooC()
    )
}

it complains that each class is not a

Foo

but a

FooA

FooB

and

FooC

. I would have thought that since they all implement the interface

Foo

it would just work?