if (data in selectedItems) {
    selectedItems.remove(data)
} else {
    selectedItems.add(data)
}

It is a better way to write this type of condition in Kotlin ?

selectedItems

is an arraylist and

data

is an object of arraylist type

Is it possible to make sure a type parameter is not

Nothing

at compile time?

So we have

@JvmSynthetic

to hide Kotlin functions from Java users, however, we have no equivalent

@JvmOnly

(or whatever it would be named) to hide definitions from Kotlin. I tried

@Deprecated("Java only", level = HIDDEN)

but it's hidden in Java afterwards as well if you use IntelliJ. 😛 Any known workarounds for this or is a feature request the only possible thing?

Why does the compiler give me the error

TypeMismatch

in the

onCreateViewHolder

for both branches of the

when

? Return type is listed as the sealed class

BaseHolder<PossibleRow>

and the return types are both subclasses of the sealed class.

sealed class PossibleRow { /* objects A, B defined here */ }

sealed class BaseHolder<T: PossibleRow>(...): RecyclerView.ViewHolder(...) {
  class AHolder(...): BaseHolder<PossibleRow.A>(...)
  class BHolder(...): BaseHolder<PossibleRow.B>(...)
}

class LiftGroupRowAdapter {
  override fun onCreateViewHolder(..., viewType: Int): BaseHolder<PossibleRow> {
    return when(viewType) {
      0 -> BaseHolder.AHolder(...)
      1 -> BaseHolder.BHolder(...)
      else -> throw IllegalStateException("invalid viewType")
    }
  }
}

Hey, which channel is best place for giving feedback for kotlin ide plugin 1.3.70-eap-184-Studio-4.0-1p? Specifically about code formatting?

Hey! I want to add better shutdown handling to my project by adding hooks to when signals like SIGINT and SIGTERM are sent but I see no way of registering hooks for those. A multiplatform solution would be the best ofc, but a JVM only one suffices for now.

I updated a 1.3.50 project to 1.3.61 and suddenly

javaClass.getResourceAsStream

returns null, any idea? I can see the file in the jar when I open it, I don't know what's happening

Hi Team, I created project on Kotlin Native, I am trying to use iOS pod library in Kotlin native but facing some issue, Can you please have a look on my question on stackoverflow and reply to me here "https://stackoverflow.com/questions/60126503/how-to-add-thirdparty-ios-pod-library-into-kotlin-native-project-getting-error"

This message was deleted.

A bit off topic, but I have been trying to use Jetbrains mono font to write some Kotlin code with the Atom editor. I have been looking and looking and can't find a way to turn off ligature (which unfortunately changes the alignment of my code). Any idea how to do that?

Somebody tried to build plugin based architecture, how should it be implemented? I thought to make a common interface's repo and then pull it on every plugin and then implement that, then call the core(main) app for adding the plugin and run it. But how should the plugin be restricted to some area, such as protection from potentially destroying or hijacking the core app? Any thoughts on this topic?

whats wrong with this code? why isActive not detecting the cancel https://pastebin.com/UcYmAAJj

Someone who understands callbacks and wants to help with this little problem:

Hello, World! Are there known bugs where the Kotlin compiler never ends? I'm in this situation and don't know what to do.

I cannot get my IDEs (AS nor IDEA) to display jdk sources, it shows the decompiled classess (therefore without documentation/highlighting), any idea how to fix that?

What does this type mean exactly and in what scenario is it use ? "Function<*, *> means Function<in Nothing, out Any?>."

People keep saying that null safety is one of the important design philosophy of kotlin but I have no idea how it applies in real life code:

/* Case A: java-style */
val result = repository.select()
if (result != null) {
    doSomething() // business logic
} else {
    doSomethingElse() // business logic
}

/* Case B: Kotlin style...? */
repository.select()?.also {
    doSomething()
} ?: run {
    doSomethingElse()
}

/* Case C: Kotlin style... + better job security through code only the creater can understand? */
try {
    repository.select()!!.run {
        doSomething()
    }
} catch (NullPointerException e) { // or whatever it was that catches not null assertion error
    doSomethingElse()
}

What is the better solution here? Obviously we can't make repository.select return non nullable type because that will result in an exception anyway. Business logic requires a different action for nonexisting row, and the only way to do this is either catch an exception, use obscure code with

.also

and

?:

, or use plain old java style code. Is there any other solution to this?

is there anywhere

kotlinx-serialization

example for

protobuf

on

jvm

?

is there any image processing library for kotlin? like jimp in node js

quick general question - is there a good tiny library for getting a human readable representation of the difference between two strings?

Is there a way to constrain the value of an inline class? Say, for example, I wanted to create an inline class

NonZeroInt

. I can do something like throw in

plus

,

minus

, etc. if the result ends up being 0...but how can I prevent the instance from being initialized with 0? I can't do an init block to verify it, and have to expose the primary constructor. I tried looking at

UInt

, which prevents you from assigning a negative number to it, but how does it enforce that? The primary constructor takes in an

Int

.

Hi, I have an issue with transient fields not being initialized after jpa saves the entity and get the value back. The reason of this is that kotlin is generating a default constructur with no params that calls super() when there is at least 1 constructor field without default value. If I define defaults to all my field in the primary constructor, then kotlin is not generation the default constructor with no params calling super() ans hence my transient field is being initialized well data class Person( var name: String){ @transient private val id: MyId = MyId() // after repo.save(person); this is not being initialized. id is null } fix data class Person( var name: String = “”){ //creating default values fix the problem @transient private val id: MyId = MyId() } Is this a bug?

Really loving learning Kotlin, laptop needs a sticker. Anyone know where I can get some Kotlin swag?

Is there something like Sealed Inline Class?

I have complex logic in nested foreach loops that is adding items to my collection. It smells that I need to call

list.add(item)

everywhere. (I will use simple example) I’ve tried to replace

(0..3).forEach {
    list.add(it)
}

with

list.add(
    (0..3).forEach {
        it
    }
)

However, it doesn’t compile. Is there a way to achieve it?

first try

I have a string template that will be read in from a file, so I can’t do regular $-interpolation on it. For example, the template might be “20+%1+5”, and I will want to substitute a value at run-time for “%1". Should I just use

String.replace()

or

String.format()

, or is there a more elegant solution in Kotlin than there would be in Java?