Lets say I have this

class Preference<T : Any> private constructor(
        val key: String,
        val default: T,
        val type: KClass<T>
)

// Extension Function
fun getPref(): T { // This should be a nullable generic set by the preference
    // parse and return pref
}

Now, not every preference is not-null. So how can I omit

<T: Any>

to get to

<T>

so the preference itself can set itself nullable only via its type generic? The problem is that KClass does not like <T> and requires <T: Any> is there any smart way to get a not-null type generic from a nullable one? Or a reified function way to handle that?

Why does the following code compile?

fun <T, R> Result<T>.letIfSuccess(
    block: (data: T) -> Result<R>
): Result<R> = when (this) {
    is Result.Failure -> this
    is Result.Success -> block(this.data)
}

letIfSuccess returns

Result<R>

, but returns

Result<T>

when first branch of when statement is met. I would expect it to give it a compile error, as

Result<T> !is Result<R>

.

I have the following

class Function1<A : Number, R : Number>(val func: (a: A) -> R) {
    operator fun invoke(a: A): R = func(a)
}

why

::invoke

seems to require a parameter of type

Nothing

here:

when(val f = t.function) {
    is Function1<*, *> -> f.invoke(stack.pop()) // Type mismatch: required Nothing
}

Because of the

<*, *>

? I cant specify anything else because of type erasure this works though

is Function1<*, *> -> (f as Function1<Number, Number>)(stack.pop())

Hi, is there any Jmeter alternative written in Kotlin ?

Is there any way to say to the compiler that use smart cast without having to use the variable assignment?

Hello I have a class like this :

class MyResponse : ArrayList<MyResponseItem>

How do I create an object of MyResponse with a list of MyResponseItem?

Hi, I’m curious if this can be rewritten with

when

block (

hasMaxRole

is extension method on my

User

data class):

if (loggedInUser.hasMaxRole(<http://Role.NO|Role.NO>_ROLE)) {
    ResponseEntity(HttpStatus.FORBIDDEN)
} else if (loggedInUser.hasMaxRole(Role.USER_ROLE)) {
    if (loggedInUser.id == id) {
        ResponseEntity.ok(loggedInUser)
    } else {
        ResponseEntity(HttpStatus.FORBIDDEN)
    }
} else {
    userApiService.findById(id)
}

I would like something like this:

when(loggedInUser) {
    hasMaxRole(<http://Role.NO|Role.NO>_ROLE) -> ResponseEntity(HttpStatus.FORBIDDEN)
    hasMaxRole(Role.USER_ROLE) && (loggedInUser.id == id) -> ResponseEntity.ok(loggedInUser as Any)
    hasMaxRole(Role.USER_ROLE) ->  ResponseEntity(HttpStatus.FORBIDDEN)
    else -> userApiService.findById(id)
}

(even with this code, I am repeating

loggedInUser

in second match since I need to call it twice in && operation)

Hi guys, I have a string interpolation in my software and I have this situation below happening:

val intValue: Int = 2498533
val foo = "<http://abc.com/$intValue|abc.com/$intValue>"
println("Foo: $foo") //Foo: <http://abc.com/٢٤٩٨٥٣٣|abc.com/٢٤٩٨٥٣٣>

But note that the interpolation is returning these non integer characters. Why this is happening? Shouldn’t it be

<http://abc.com/2498533|abc.com/2498533>

?

I have a

List<String>

and a function

f: String -> T?

and would like to apply

f

to each element

s

of the list in order until

f(s)

is non-null, returning that

f(s)

. If

f(s)

is null for all values,

null

should be returned. Here’s an ugly implementation:

fun g(list: List<String>): String? =
    if (list.isEmpty()) {
        null
    } else {
        f(list.first()) ?: g(list.subList(1, list.size))
    }

Can someone suggest a more elegant way? Here’s the code, if you’d like to play with it. https://pl.kotl.in/mByy6tkph

how to clear a ByteArray? var aob = ByteArray(1024)

hello, anyone here?

Hi, Yesterday I discovered that kotlin allows this sort of code:

data class Thing (
    val prop: String
) {

  private fun getProp(): Int = 5
}

Although this code won’t compile:

data class Thing (
    val prop: String
) {

  private fun getProp(): String = "a"
}

with error “Platform declaration clash: The following declarations have the same JVM signature (getProp()Ljava/lang/String;)” The first one compiles successfully, and the

getProp

function can be either

private

or

public

. In Java, the same code won’t compile:

public class Test {

  private String prop;

  public final String getProp() {
    return prop;
  }

  public void setProp(String prop) {
    this.prop = prop;
  }

  private final int getProp(){
    return 5;
  }
}

With error: “‘getProp()’ is already defined in ‘com.ni.monday.model.domain.webhooks.events.Test’” So why is it allowed in Kotlin? The consequences of this is this bug, I opened yesterday on #jackson-kotlin : https://github.com/FasterXML/jackson-module-kotlin/issues/341

This is not a bug. It's just that kotlin is a different language from java.

do you think the factorial can benefit from a

tailrect

function?

var result = 1
for (i in 1..a)
    result *= i
result

Is there a built-in contract for verifying that, if a Map contains key

k

then

Map[k]

is non-null? Or do I need to write my own?

Whenever I upload an image from my gallery the image always return rotated. How can I rotate these pictures back to the appropriate way?

I'm using a singleValueEventListener and I just want to return that data everytime it changes

promoCodeGenerationCountExceeded

is false when it should be true

message has been deleted

Is it possible to hide fields from toString in data classes? I have a problem where one class has a list objects. Each object contains a reference to the first class. This is causing a stackoverflow in toString

Trying to understand coroutines better, if you use delay inside of a coroutinescope will it carry on doing other jobs on the thread during that time? Or what is the difference between delay and thread#sleep

I want to use Kotlin Experimental Time in my project, but its a pain having to annotate so many places with

@ExperimentalTime

, is there a way to disable this requirement?

Does anyone have a recommended tool for generating null-safe (such as one that uses lateinit or requiresNotNull) builders for kotlin classes? I’d normally use named arguments and default params, but I need a builder to support interop with Java.

I have spend 2 hours today figuring out why my code wasn't behaving. I got lucky cause I noticed I was running code in file I shouldn't have been in, and remember I read somewhere that interface delegation with default methods don't get delegated. I can't really find any information on when/if this issue will be fixed.

Does it exist in Kotlin ??? like in Scala to delay function implementation?

Has anyone run into the problem of extremely long compileKotlin steps? I have a ktor app that is taking 10 mins in the compileKotlin gradle step. On occasion, builds will take the normal amount of time, but more often than not, I am stuck in the hell of a 10 min build time -- even after simple code changes in a single file I have a 16 core, 64GB MBP, so it is not a question of compute resources. I am able to rebuild other Kotlin projects in the expected amount of time. It is just a single ktor app that is giving me grief. Incredibly, the same project was compiling fine a few days ago. I have tried multiple JVMs and multiple machines (my travis builds are timing out after 11 mins). I have also tweaked every gradle build option I could find, but to no avail. Any thoughts or ideas would be greatly appreciated.

does kotlin provide any list implementation that can do efficient (constant-time) cons/cdr, for use when designing tail recursive functions that operate on lists?