“consider default value is $0.00, if the customer types in 1, we will display $0.01 If they type in another 1, we display $0.11. If they type a 0, we display $1.10” how to achieve this in kotlin edittext?

I have a question regarding how to model the following. I have a data class representation of all the supplied data.

data class Activity(
	val startTime: LocalDate
	val endTime: LocalDate
	val directTime: Int
	val indirectTime: Int
	val travelTime: Int
	val quantity: Int
)

It's unsure how this class will be used, but at least, this is the absolute truth of the class. Later on, someone says: I want to use a specific predefined version of this activity, a data class that looks like this:

data class SpecificActivity(
	val executionTime: LocalDate
	val duration: Int
	val quantity: Int
)

but somehow backed by the original, hence; executionTime is just startTime, duration is just endTime - startTime in minutes , and quantity is still the same, the other fields are ignored. But I also want to let everyone know, in the model, that SpecificActivity IS an Activity, just not with the represented fields. such that someone can easily say: I want this SpecificActivity, but I want that other version of it (SomeOtherSpecificActivity, that might not have dates, for example.) I know about backing fields, sealed classes and the like, but none of them really do what I want.

play.kotl.in/kotl.in/try.kotl.in compiler is down (timing out)

Why does type inference fail for

extract

here?

object Container {
    val contained = mutableMapOf<String, Any>()

    inline fun <reified T> extract(name: String): T = contained[name] as T
}

class Foo {
    val bar: String by lazy {
        Container.extract("Bar")
    }
}

Because

lazy

is declared to return a

String

, shouldn’t the inferred type

T

also be

String

?

I have a variable that I'm initializing with

val something: Something by lazy {}

but for unit testing I need to be able to mock retrofit. I'd also prefer that the code for building the Retrofit be encapsulated in the class itself. I have a few ideas but I'd like the Kotlin idiomatic way of doing it.

In our code we often have some iterable on which we do several

map

and

filter

. We have recently gone through the code wiht a profiler and this led us to use

asSequence

so that we have

myIterable.asSequence().map { .. }.map { .. }

. Why the compiler cannot make this optimization automatically? It’s quite obious that I’m not using the intermediate object.

Is there a better way to suppress warnings about unused parameters in callbacks than there was in the answer to this 2015 Stack Overflow question? https://stackoverflow.com/questions/29046636/mark-unused-parameters-in-kotlin/29046925

Hey, hope this isn't too annoying!

nvm found the issue

does anyone know of wrappers for material-UI or bootstrap around kotlinx-html ? seems like what i find is all just for react or in kotlin-js context in this project i'd like to reduce the amount of js and just generate html and css using typesafe builders

is there a way to iterate alle subclasses of a sealed class? i mean... in the end arn't sealed class enums on steroids? i can do that with enums 😉

why launch by itself doesnt exist for example when you say launch{} it says

unresolved reference

https://twitter.com/kotlin/status/1227993505332682753 Did you know? Properties declared as 'val' can be overridden as 'var', and property setters can be made less visible than their getters #KotlinTips https://t.co/Ba1LxBF4dI https://t.co/U4Dpqo1Mlz https://t.co/dHP8O6YHOI Twitter

I wonder why exactly

private const val

symbols are kept in the bytecode. I guess for reflection but what if this is not required? There should be some kind of annotation to drop these symbols after they are inlined everywhere, no? (Maybe should post this in #language-proposals but wanted to first hear if someone has another reason than reflection to keep them.)

Had an unwelcome surprise with inline functions the other day. I had a custom inline function with multiple branches that would execute a functional parameter. I didn't realize until looking at the bytecode that functional parameter arguments were actually written out once each time that the functional param is referenced. E.g.:

inline fun myInlineFun(myCase: Boolean, crossinline doSomething: () -> Unit) {
    if (myCase) {
        doSomething()
    } else {
        println("Start")
        doSomething()
        println("End")
    }
}

The argument for the

doSomething

param is written out twice in the resulting bytecode. Logically, this makes perfect sense to me -- unless there were a simple way for the compiler to remove the branches (which it does actually do if the condition is trivial, by the way), then the function must be written twice. It can have dangerous implications for uses though, especially if a caller attempts to use a long functional param. I didn't notice a kotlinc or IntelliJ warning/inspection for this. Not sure if there are any other tools which would provide one. Anybody else run into this?

Is there anything such as a Kotlin Workspace? When programming in R using RStudio, one can keep a computation in memory, and then continuously write code to use that computation. In Kotlin we usually execute everything, and we don't save the in-betweens. For instance, I want to create a table from data I pulled from the web, but I forgot to add a comma. I have to pull all the data from the web again to use it. Of course I could "cache" it in a file or something, but I'm wondering if there's such a thing already.

This message was deleted.

How do I dynamically get my subclass name from abstract class? Example I want to replace

GetSubclassNamehere???

with whichever subclass called the someMethod().

abstract class A<T> {
    fun someMethod(item: T?) {
        try {
            if (item == null) {
                println("GetSubclassNamehere??? received null item")
                return
            }
        } catch (e: Exception) {
        
        }
    }
}

class B : A<String>() {
}


fun main() {
    val b: A<String> = B()
    b.someMethod(null)
}

How do I get my Logger to print subclass name instead of abstract class name? https://stackoverflow.com/q/60217253

does anyone know how I can add a element to the

notes

array in the following json object?

val msg = json { obj( "a" to "b", "notes" to array() ) }

Also asked this in Klaxon, but don’t know if that channel is too active

I don’t know what

json

or

obj

are here, so it’s hard ot say what’s possible. But you may be able to do something like:

val msg = json { obj( "a" to "b", "notes" to mutableListOf() ) }

(msg.array("notes") as MutableList).add(element)

I've found this in the source code

// exposed as public
@PublishedApi
internal fun timer(name: String?, daemon: Boolean) = if (name == null) Timer(daemon) else Timer(name, daemon)

docs of published contains:

When applied to a class or a member with internal visibility allows to use it from public inline functions and makes it effectively public.

the question is: since it's internal why should I care about not making breaking changes to the declaration? It's just there for the purpose of chopping up big public inline functions, no? so published internal inline fun is like a private fun in class, right?

Job search question: How would search for opportunities to work remotely as a Kotlin developer? I can do both Android and Backend. I've been on generalists website like Remote OK but they not really focused on Kotlin jobs in europeans timezones

becoming a backend kotlin developer leads to jobless?

🤔

Is it possible to use

when

on a reified generic type?

inline fun <reified F : Foo, reified B : Bar> convert(input: F) : B {
when(B) {
Bar1 -> {}
Bar2 -> {}
}

Is anyone try to compile Kotlin Multiplatform Projects on the Windows (Example https://github.com/jinqian/kotlin-native-chifoumi)? looks like problem is still here, tested on JDK 8 and 13 https://github.com/JetBrains/kotlin-native/issues/1846

how can I improve speed of

(min..max).toList

it takes 5000 .. 50000 -> 6.516391 s to generate

Hey here, anyone can help me with a gradle script ?

any simple thread-based concurrency "framework" for a producer(s) -> queue(s) -> consumer(s) pattern?