Is there any way to use this

sealed class

to use it as a parent?

sealed class ClientName {
    data class normalClass(val name: String) : ClientName()
    object SpecificObject : ClientName()
    object AnotherObject : ClientName()
}

So now, I need to have the same objects and class but different output, so on my extension function : That is something like this :

fun ClientName.toText(): String = when (this) {
    is ClientName.SpecificObject -> "Print1"
    is ClientName.AnotherObject -> "Print2"
    is ClientName.normalClass -> if (this.name == "") "hello" else "Bye"
}

So now I see that I'd need different types, it means that

SpecificObject

,

AnotherObject

and

normalClass

are goinna print different things depends of the type, so what I thought is create another

sealed class

like :

sealed class Type1 : ClientName()
sealed class Type2 : ClientName()

And then in that extension

toText

check if is

Type1

then do X and if it's

Type2

do Y. But I do not know how to do it to get the same values and same clases as the

ClientName

what I'm missing?

if (seekTo in (window1.first..(window1.second - rowsize)))

does this compile to something other than

it >  min and it < max

??

I was waiting for news on Kotlin inline classes in Kotlin 1.4, but nothing in the blog post 😥

I have a code like this: https://pl.kotl.in/5vZUgXStV I expect that it will print

true

. However,

ClassCastException: java.lang.Long cannot be cast to DogId

is thrown. Is it a bug in kotlin? Or maybe I’m using inline classes incorrectly?

how do I use Kotlin to kill the coronavirus?

Tired of having to annotate a bunch of methods with

@ExperimentalStdlibApi

to a bunch of methods, I changed my Kotlin Compiler Preferences in AndroidStudio to include

-Xopt-in=kotlin.ExperimentalStdlibApi

in the “Additional command line parameters” (as per the instructions here: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-experimental-stdlib-api/). However, I’m still getting build failures when I remove the annotations and depend on the global command line parameter. What am I not getting?

im planning to give up my handler (account) [ kotlinlang] to someone , am i allowed to do that?

any idea why

tasks.withType<KotlinCompile> {
    kotlinOptions {
        freeCompilerArgs += "-Xjsr305=strict"
        freeCompilerArgs += "-Xopt-in=kotlinx.serialization.ImplicitReflectionSerializer"
        jvmTarget = "1.8"
    }
}

results in

w: Flag is not supported by this version of the compiler: -Xopt=in=kotlinx.serialization.ImplicitReflectionSerializer

? (kotlin 1.3.61)

Hi! Can anyone explain why this code doesn't work?

typealias F<T> = (T) -> T

fun test() {
  val id: F<*> = { it }
  consume(id)//error here
}

fun <T> consume(v: F<T>) {
}

It looks like all should be fine, but the compiler tells me

Type mismatch: inferred type is Any? but CapturedType(*) was expected

. I thought that the star means "some unknown T", am I wrong?

I wrote a library that I'd like to make publicly available, so people can easily use it with gradle/maven/ect. However I am completely lost with what i need to do now. I looked into MavenCentral/JCenter/Bintray but they all seem to assume that I am part of some organization, which I'm not. I also don't have a website so I don't even know what I should use as my "group id". can someone help me get started?

too many channels about testing. which one is the general channel about testing not related to a framework?

we have decided to use kotlin for our startup for mobile. is anyone using it production? for some time. we have used Xamarin (F#) before

I have question about cli app development. I created the #clikt channel for questions about that particular framework. I don’t see any general cli app development. If there is a channel about that please let me know

I need a little help with understanding if multi-threading might be causing me some problems with this class. Here is an example:

@javax.inject.Singleton
class SpecificWork @Inject constructor() {

  private var cruncher: Cruncher? = null

  @GuardedBy("this")
  init {
    initCruncher()
  }

  @Synchronized
  private initCruncher() {
    // io work initialization
    cruncher = try {
      IOCruncher.init()
    } catch (e: IOException) {
      null
    }
  }

  fun doWork(): Result? {
    if (cruncher == null) {
      return null
    }

    // do work
    return Result("done")
  }
}

This

SpecificWorker

is provided via Dagger for dependency injection, but there could be many threads calling into it at the same time. I’m wondering • Is there a case where the

doWork()

started executing before the

initCruncher()

was able to assign the

cruncher

? Making the

cuncher

null and failing early?

how to convert this MainList [ obj1, obj2, obj3, obj4, obj5, obj6, obj7, obj8, obj9, obj10 ] TO [ obj1 , obj2 , obj3 ] [ obj4 , obj5 , obj6 ] [ obj7 , obj8 , obj9 ] [ obj10 ] anyone understand me ??

Hello. Can anyone explain to me, why some simle functions on Iterable return list and not Iterable subtype it was applied to? For example:

inline fun <T> Iterable<T>.filter(
    predicate: (T) -> Boolean
) : List<T>

If I chain multiple functions, say, using Set, it is simetimes uncomfortable to call

toSet()

each time the list is returned.

Does anyone have an answer for Heinz? https://twitter.com/heinzkabutz/status/1242722285712216064?s=20

is there library that pretty prints java or kotlin objects via reflection? something like http://www.lihaoyi.com/PPrint/

Hi guys, why this happens? And what is the right way to fix it?

How does the

language-version

compiler option works? Does it modify the outputted bytecode & metadata to be compatible with another version?

what is the best of creating a generic object that has an argument in its constructor. For instance if I just need to create a new object that the class does not have arguments in its contructor I would be able to make

T::class.java.newInstance() // Where T is a generic type

But, if I want to make an new object that need to receive an argument. The usage of this would be in a recycler view where I have different view holders but each one has a constructor with only one argument. like

inner class ShortTextViewHolder(
        private val viewBinding: ItemRowFormFieldTextBinding
    ) : RecyclerView.ViewHolder(viewBinding.root), FieldViewHolder {

        override fun configureWith(field: FormField) = viewBinding.run {
            with(field) {
                textFieldName.text = label
                textFieldDescription.text = description
            }
        }
    }

So basically, I would like to simplify this

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
        val view = ItemRowFormFieldTextBinding.inflate(parent.inflater)
        if (viewType == ITEM_TYPE_SHORT_TEXT) {
            return ShortTextViewHolder(view)
        }
        return LongTextViewHolder(view)
    }

By calling a Factory like

factory<LongTextViewHolder>(view)

or

factory(view, myPossibleTypes[viewType])

where

myPossibleTypes

would be a list of the types I can instantiate

If I had a data class that looks like

data class Sample(val foo: Number)

and the following example map that I may not know until runtime

mapOf("foo" to 1, "bar" to 2, "baz" to 3)

. How can I extract just the value that's relevant to the

Sample

data class and build it when I don't know if the field in question will be present?

Looking in the flow builder I was confused by the type signature of the block param

suspend FlowCollector<T>.() -> Unit

In general what is the meaning of Type.()?

How would I transform this list of pairs:

val pairs = listOf(
    Pair("A", 1),
    Pair("A", 2),
    Pair("B", 3)
)

to this map:

mapOf(
  "A" to listOf(1, 2),
  "B" to listOf(3)
)

Is there a function like

Iterable.sum()

that multiplies instead? I know I can use reduce to get the same effect, just looking for a cleaner way to code this.

why is a

Sequence

not

Iterable

?

hello, i have a question related to inheritance and data classes in my specific case i receive the same object as json once with an enclosing data wrapper, and once in an object which has a list of that type:

case 1: { data: {props.....} } -> StoredVehicleUserSingle
case 2: { data: [ {props.....}, {props.....} ]  } -> StoreVehicleUsers with a list of StoredVehicleUsersList

so far i have solved it like this:

data class StoredVehicleUsers(
    @JsonTypeInfo(use = JsonTypeInfo.Id.CLASS, defaultImpl = StoredVehicleUserList::class)
    @JsonProperty("data") val vehicleUsers: List<StoredVehicleUser>
)

/**
 * we need to implementations for this for:
 * [StoredVehicleUsers] its [StoredVehicleUserList]
 * if its a single [StoredVehicleUser] we receive its [StoredVehicleUserSingle]
 */
interface StoredVehicleUser {
    val vehicleId: String
    val userId: String
    val role: String?val roleTimestamp: Date?
    val resetRole: String?
    val resetRoleTimestamp: Date?
}

@JsonTypeInfo(include = JsonTypeInfo.As.WRAPPER_OBJECT, use = JsonTypeInfo.Id.NAME)
@JsonTypeName(value = "data")
internal data class StoredVehicleUserSingle(
    override val vehicleId: String,
    override val userId: String,
    override val role: String? = null,
    override val roleTimestamp: Date? = null,
    override val resetRole: String? = null,
    override val resetRoleTimestamp: Date? = null
) : StoredVehicleUser

internal data class StoredVehicleUserList(
    override val vehicleId: String,
    override val userId: String,
    override val role: String? = null,
    override val roleTimestamp: Date? = null,
    override val resetRole: String? = null,
    override val resetRoleTimestamp: Date? = null
) : StoredVehicleUser

i think the solution is fine, the only thing that bugs me, is that i am repeating all properties in StoredVehicleUser, StoredVehicleUserSingle and StoredVehicleUserList, despite they are same. the implementations must be data classes to have euqal and hashcode. but if i use inheritance i actually must list all props in subclasses again and pass them to Super constructor. also a data class must have at least one constructor argument How can i do this better? (edited)

Is there a library for doing combinatorial optimization?