Architectural question: I’d like to create an ecommerce where merchants could sign up and sell their products. So one website with multiple merchants. Now I’d like to be able to pay each merchant directly each time a product would be sold from the website (and take a cut directly as well). I’m thinking when a merchant sign up, they could enter their Mollie or Braintree (for instance) account number… Which payment platform would you people recommend ?

This message was deleted.

Is it possible to call

fun foo

in this runnable example in a way that doesn't provide a value for the first parameter with a default value? The types of the first two parameters happen to be compatible, which is unfortunate (even though they're not the same!)

fun <T: Any?> a(b: (value: T) -> Unit) {
    b(null)
}

why does this not work? Why does it say T is non-nullable, even though it uses

Any?

? Can I make this work without changing the lambda param to

value: T?

?

The

b

in

a(c[0]!!(), b)

will error with type mismatch. Expected

CapturedType(out B*>)

but

B<*>

. How to pass the

b

as param? https://pl.kotl.in/VVNMv8Zso Edited: add comment

// KSerializer in my actual env
open class A<T>

// An external class from lib
class B<T>

// My serializer
class C : A<B<Int>>()
// A map to take correct serializer by arg
val c: Map<Int, () -> A<out B<*>>> = mapOf(0 to { C() })

// CompositeEncoder#encodeSerializableElement in my actual env
fun <U, T : A<U>> a(a: T, b: U) {
}

// KSerializer#serialize(encoder: Encoder, value: B<*>) in my actual env
fun b(b: B<*>) {
    a(c[0]!!(), b)
}

Error

Type mismatch.
Required:
CapturedType(out B*>)
Found:
B<*>

coming from Rust: what is the equivalent of a

Result

in Kotlin, and is it idiomatic to use it? do failible functions in Kotlin generally return error types on failure, throw, or just return `null`/silently exit?

is there a more compact way to do this?

var maybe_null = if (condition) { method_chain_that_may_return_null() } else { null }

Why

abstract

can be

inner

, but

sealed

,

data

not?

Is there a

retry

or similar for `try`/`catch`?

Hi, I'm not sure I am using the right framework for my project. I want to make an app that sends customer's orders to me by mail, and allows for payment. Can I work on the front-end and back-end with IntellijJ IDEA, or sohould I be learning something else, like android studio for front-end? Thanks a lot

is there really no way to get Kotlin to auto-infer that in

my_uint += 1

the type of 1 is not

Int

?

How is it that

inline constructors

are prohibited but there is an exception for the

Array

class implementation?

is there any way to check maps has all values null? val m = mapOf(“s” to null, “a” to null) Not working >> println(m.values.isNullOrEmpty()) working >> println(m.values.all{it == null}) better way >>?

Is it possible to get an insight into Kotlin development strategy? I really don't understand some of the decisions regarding the development and advancement of Kotlin. Just an example: in my opinion Kotlin multiplatform is one of the most important Kotlin feature, and yet it is full of blocker bugs and incomplete core features (eg. Gradle composite build). In the meantime, the team spends a lot of time developing minor features, like the new range operator. Value classes: it is a great feature and I personally like and use them a lot, but are they really worth the enormous amount of work put into them? The target platforms should and will optimize them in compile/runtime anyway sooner or later. I don't want to sound offensive, I just really want to understand the priorities, and understand why it is not possible to do a feature freeze until the current functionality has much less bugs...

Hi, is there an idiomatic way to attribute a value to a variable if this variable is null ? Other than a

if

It seems there is not in Kotlin infix function without parameters. I mean, we can not in some way implement something like: fun main() { println(1 m) } infix fun Number.m() = Meter(this.toDouble()) class Meter(val value: Double) Or exist some trick?

Hi,How it is possible to return array of items if there is when inside, how should I modify the else bracnh to get it working fun printAll(type: Int): Array<String> { // 1 return arrayOf( when(type) { 1 -> "one" 2 -> "two" else -> { "three","four" } } ) }

Hey I was wondering how I enable Kotlin 1.7.20 features? I set my JVM version to 1.7.20 in the gradle build

kotlin("jvm") version "1.7.20"

Trying to use data objects but run into this error

The feature "data objects" is only available since language version 1.8

, thanks in advance.

I have

foo: String

and

bar: List<String>

. What's a clever way to return true if

foo

starts with (or I guess

contains

works too) at least one string in

bar

?

How do you use delegation and a where clause?

interface F
class B<T>(t: T) : F by t where T : F

why does the following code snippet

"foo" > "bar"

magically works in Kotlin REPL and returns a boolean instead of throwing an error or exception? how is it even possible to "compare" strings this way when the same code in Java does not work at all?!

When is a nullable value not nullable? Somewhat confused by these two messages in Android Studio - in the middle of a

?.let { }

block, no less. The value from the repository is hypothetically null, but I thought the let block would have handled that.

How can I pass value class parameter from Java? IDEA suggests me using the underlying type but it's just a compilation error.

I have a function like this at top-level of a Kotlin file:

package mypackage

fun main(args: Array<String>) {
    // ...
}

Usually used as program entrypoint in JVM. However, when I try to call it from another Kotlin module:

import mypackage.main

class MyClass {
    fun myMethod() {
        main(arrayOf("foo", "bar"))
    }
}

I get this strange error:

Kotlin: Overload resolution ambiguity: 
public fun main(args: Array<String>): Unit defined in mypackage
public fun main(args: Array<String>): Unit defined in mypackage

any good libraries for generating json from a json-schema?

Could you please help me work this out? I have three buttons and when I select one, I want the other two to be disabled until I unselect it. I can't figure out out to put that into code. I thought that this would work (at least for the first button):

if (option.id == 0) {
                for (o in listOfOptions) {
                    when (o.id) {
                        1 -> enabled = false
                        2 -> enabled = false
                    }
                }
            }

But all my 3 buttons are disabled when I do this... 🤔

isn't this decidable somehow?

sealed interface Foo
sealed interface Bar
sealed interface Thing {
    object ONE : Thing, Foo
    object TWO : Thing, Bar
}

fun main(){
    val thing: Thing = Thing.ONE
    if(thing is Foo && thing is Bar){
        // This can´t happen
    }
}

I get string:

name: tom, weight: 50, age: 21

How I can get value

name

,

weight

,

age

?

Hi, I read that if I want two functions to run consecutively, they have to be suspend functions. So I turned

function1 ()

and

function2 ()

into suspend functions, and set them up like this:

val scope = rememberCoroutineScope()

    ElevatedButton(
        onClick = {
            scope.launch {
                function1 ()
                function2 ()
            }
        },

The problem is that I need for function1 to be completed before function2 can start. So if I put a 1 second delay between the two, my app works as expected, but if I don't it seems function2 does not wait for function1 to complete before it starts. Is there a way to get f1 to finish before f2 starts without adding a delay in between the two?