val x = if (y != null) y else {
    <http://log.info|log.info>("bla")
    z
}

vs

val x = y ?: run {
    <http://log.info|log.info>("bla")
    z
}

Hi all, I reached the point where I would like to share code between two projects of mine. I assume it must be somehow possible to extract it into a (nonpublic) library and add that as a dependency in gradle. Is there a good guide / tutorial about how this can be achieved?

Hey, do I need to do something like this for extending?

class NotAuthenticatedError(
   override val message: String,
) : Error(message = message)

I mean can’t I basically use the message immediately because it is extending?

I also would like to ask how can I forward annotations For example: Instead of doing;

@PreAuthorize("hasRole('user')")

I would like to do

@UserOnly

What’s the reason that I cannot typealias a nested class?

typealias BR = foo.bar.base.R

if I then use

BR.

I don’t see

string

,

drawable

etc I can only do

typeealias BR_string = foo.bar.base.R.string

typyealias BR_drawable = foo.bar.base.R.drawable

etc, which is stupid

Hi all - I'm working through the JetBrains Academy course on Kotlin and I have a dumb question. I'm at the early point of looking at the output of

val result = println("text")
println(result)

text
kotlin.Unit

One of the practice questions asks about the Magic Of

println

and it implies that the value of

result

is

Unit

. While that's true, what's "text" doing in the output? Maybe this is something that I don't need to be worried about (and I'm not) but I'm curious why. println is called twice, once for "text", and then a second time for

println

itself, and the type value of the

println

function is

kotlin.Unit

? Is that true for all functions? Just

println

? Thanks for any clarity you're willing to share!

I am having some trouble with visibility modifiers. Basically I want a public getter method with a private setter for subclasses of a parent class. The issue is if that parent class has a private variable it is not able to be set from the child classes so I have to have the parent have a public variable for the child classes to use it but now the var is public so the getter is useless. In Java this was possible with the package-private modifier which in Kotlin has been changed to module-private so do I really need to create a new module just to hide some

vars

?

is there some heuristic whereby it makes sense that collections.last() is a function but size is a property?

and on the math side, absolutevalue is a property of Double, pow is a method of Double, and sqrt is a standalone function in the math package

is there any way to get html syntax highlighting on a kotlin template string in intellij?

Hello guys, hope you can help me with this. I have a function that deletes an element of a list, something like:

fun delete(id: UUID) = list.removeIf { it -> it.id == id }

And I want to: • If the element was removed, don’t return nothing. • If the element was not found, return exception For now I have something like:

fun delete(id: UUID) = takeIf { list.removeIf { it -> it.id == id } } ?: throw NotFoundException(id)

But this still returns a true.

Hello I want to write a regex the checks if the string contains the following characters ' " | \ / <>:

"Team's<>".contains("/[\"'\\/\\\\<>;|]/;")

Hi all - another "what are the expectations here?" question based on a question in the JetBrains' hyperskill Kotlin course. I have a question that asks: "what are the expected inputs for the following snippet of code:"

val scanner = Scanner(System.`in`)
val s1 = scanner.nextLine()
val s2 = scanner.nextLine()
val num = scanner.nextInt()

The answers are roughly: a )

ABC DEF
123

b )

ABC
DEF 123

c)

10
ABC
3

d)

ABC DEF 123

Looking the behavior in kotlin file locally, the only answer that doesn't throw an error is

a

, but not according to the course page. Is this a Kotlin version issue? A JVM issue? Apparently the correct answer is

c

but the first Int is confusing me. Any hints or clarity would be most appreciated! Thank you!

#getting-started - I am new to Kotlin and trying to absorb as much as possible. I have a requirement where I have a Multi-Level List that I need to parse up to 4 levels. List<List<List<List<String>>>>. The typical way would be using 4 for loops and keep iterating, but I am looking for a smarter Kotlin way of doing it. Could you guys please help me get there?

for(a in As){
    for(b in Bs){
        for(c in Cs){
            for(d in Ds){
                
            }
        }
    }
}

Another train of thought I have is to use flatMap() to flatten the last loop and drop the loops from 4 to 3. But there too, am getting beaten up by Kotlin syntax. Any help is appreciated! TIA 🙂 EDIT: Sturcture is of complex type in nature:

data class A(
    val b: List<B>
)
data class B(
    val c: List<C>
)
data class C (
    val d: List<D>
        )
data class D(
    val string1: List<String>,
    val string2: String
)

Are there other languages with feature similar to Kotlin's inner claseses?

Why does this error occur? I thought the

contract

should prevent it

val invoke: suspend ()->Unit = fun(){}

Shows this error is it possible to declare suspending anonymous function with fun keyboard. I am also aware of suspending lambda that's not my question. Thanks in advance.😇 error type mismatch: inferred type is () -> unit but suspend () -> unit was expected (line_27.kts1️⃣32)

In this snippet, sequence{} knows its in the

parens

rule if you check prop.name in getValue or provideDelegate, but is there a way the resolve() call could get access to this information somehow? I checked the stack trace and couldn't really find anything that could give this information

I am having trouble understanding some code I saw of the form:

fun myfun: Boolean {
  return foo?.stringProperty.isNullOrEmpty()
}

It seems to me that this would return

null

, which is not

Boolean

when

foo

is

null

. Why is the above code legal?

I’d like to create a scheduler app that contains a list of events. Each event has a

startDate

and an

endDate

. I’d like to determine which events overlap so I can place events in a different column. Is there a way to apply some sort of

groupBy

function to accomplish a way for me to group them?

Which type would you use to represent a single digit

[0-9]

? 1️⃣ Int 2️⃣ UInt 3️⃣ Byte 4️⃣ Short 5️⃣ value class of Int 6️⃣ value class of UInt 7️⃣ value class of Byte 8️⃣ value class of Short 9️⃣ value class of Char I suppose we already have the Kotlin answer, which is

Char.digitToInt(): Int

DigitFactoryContentProviderAdapterBridge

Please can someone explain what is happening here: https://pl.kotl.in/3lF-S9LUl

var check1 = true
var check2 = false
val test = if (check1) {
    null
} else if (check2) {
    listOf("foo")
} else {
    listOf("bar")
}.map { 2 }
println(test)

It seems we don’t need to use safe null on the

map

call. However, if we remove the middle branch, then we do need it:

var check1 = true
var check2 = false
val test = if (check1) {
    null
} else {
    listOf("bar")
}?.map { 2 }
println(test)

In both cases (without the

map

), the type of

test

is

List<String>?

Hi, I have a typescript application. I want to create a Kotlin based application basing the same ts contracts/states. So I’ve started converting them from typescript to kotlin using custom scripts. While doing so, I’m facing a few challenges and one of them is to identity the kotlin’s equivalent implementation of typescript’s optional property, which is denoted by

?

in states. For example: My contract in ts is -

export interface A {
    id: number,
    name: string,
    imageId?: number,
    modified?: string,
}

In the interface A, the imageId and modified properties are optional. How do we denote the same functionality in kotlin’s classes?

Can I deprecate or warn if a

fun

in used in kotlin but issue no warning in java? We created a “bridge function” for java which should be avoided in kotlin code. I thought it would be nice to show a warning if used accidentally in kotlin code.

is it possible to generate compiler warnings when violating requirements? e.g.

value class Example(val value: UInt){
		init{
			require(waarde <= 999_999_999u)
		}
	}

obviously this doesn't work, but a range check on numbers seems trivial when you actually call constructors

has anyone found a way to force mandatory parameters in DSL other than moving them as constructor arguments?

Hi, in which cases should I use arrays instead of lists ?

Hi everyone! I want to initialize a

Boolean

variable from another one of type

Boolean?

and if the value is

null

then I will want to check if a value is present in another list and use that value for the initialization. Here is the code:

val statuses = listOf("pending", "on-hold", "auto-draft") 
   val status = "pending"
   val isEditable: Boolean? = true
   
   val result = isEditable ?: status in statuses
   print(result)

But this initialization using the Elvis operator always returns

false

, if I move the

status in statuses

to a different variable or I wrap it in a

run {status in statuses}

then the code works as expected. Am I missing something here or this is a bug? You can test the example here: https://pl.kotl.in/4QDgoNvYi