it says i cannot use it as a return type

Hello Can anyone Suggest me good Android book which i can use it from scratch.

Can DeprecationLevel of @Deprecated method in a library depend on caller's Kotlin version?

Hi. Is it possible to call scala code from kotlin?

When writing a file that is just extension functions, do you make the file uppercase or lowercase for the first letter? The context would be both in a pure Kotlin project, and a mixed project (Kotlin with Java interops).

Hi, is it possible to override a set and get function of a data class constructor var field? for example: data class Person(var name: String) I want to do something like fun setName(value: String){ this.name = value doSomethingElse() }

Hi Guys, is there a beginner’s guide to understanding coroutines and coroutine context/scope. I’m still kind of confused by how to create them. For frame of reference, I come from a CompletableFuture/ nodeJS Promise background

Kt public property is private in java Anyone who could help ?

Hello, I'm new to Kotlin but Java was the first language I learned back in 2010. I was wondering is there any binding for the python interpreter for Kotlin? I'm trying to develop an AI but also want to turn this into an app so that's why I wanted to go for Kotlin for the majority of the development and only develop the AI in python since there exists very nice deep learning frameworks. I tried searching for bindings to Kotlin for python and couldn't find anything... Basically what I'm hoping to find is something like this but for Kotlin: https://cppyy.readthedocs.io/en/latest/ I only need calling Kotlin from Python

Example in docs throws an error. Not sure if intended or not

if I enable the spring compiler plugin in gradle, do I also need to enable the all-open plugin if I want to add additional annotations to the all-open list?

hi is there a jetpack compose specific channel?

I have a simple "Observable" wrapper that I was playing with.

class Slot<T> {
   private var _value:T
   var value:T
      get() = this._value
      set(newValue) {
         this._value = newValue
         // trigger notifications here
      }

I wanted to add a variant of the

value

interface for types of

T

that are

Comparable

that would filter out no op changes. So I added the following extension:

var <T : Comparable<T>>Slot<T>.concisely:T
   get() = this.value
   set(newValue) {
      if (this.value != newValue) {
         this.value = newValue
      }
}

This works like a charm...

Slot<Int>(42).concisely = 42

does just what I want. The inner

value

doesn't get called. Where this falls apart is when I have a

T

that is an optional.

Slot<String?>("foo").concisely = "foo"

won't even compile:

Type for parameter bound T in
var <T : Comparable<T>>Slot<T>.concisely:T
is not satisfied: inferred String? is not a subtype of Comparable<String?>

I have thrown various alternate incantations at my extension to try and accomodate optionals, but nothing seems to work. Is it even doable? What am I missing? I know that I can use

==

on optional types...

Is there any way to check if a Kotlin type is immutable at compile time (i.e. with some API in

org.jetbrains.kotlin.types

or

<http://org.jetbrains.kotlin.ir|org.jetbrains.kotlin.ir>

?

Do typealiases persist after compilation?

Is it queue realization in kotlin?

Is it possible to make an extention-function that is only callable in the context off a certain type with certain type parameters?

Both invocations are marked as ambiguous, which I find very weird.

Can someone please tell why the type R below is being erased even though it is reified?

class BaseResponse<T> {
    val data: T? = null
    var someMessage: String? = null
}

class User {
    val name: String? = null
}

fun main() {
    val name = getUser<User>().data?.name
    println(name)
}

inline fun <reified R> getUser(): BaseResponse<R> {

    return if (testMessage == null) {
        BaseResponse<R>().apply { someMessage = "Some error" }
    } else {
        Gson().fromJson(
            testMessage,
            object : TypeToken<BaseResponse<R>>() {}.type
        )
    }
}

val testMessage: String? = """{"data": {"name":"Adam"},"someMessage":""}"""

Error -

Exception in thread "main" java.lang.ClassCastException: class com.google.gson.internal.LinkedTreeMap cannot be cast to class User (com.google.gson.internal.LinkedTreeMap and User are in unnamed module of loader 'app')
	at MainKt.main(main.kt:54)
	at MainKt.main(main.kt)

If I send BaseResponse<User> as R instead of just User and return R, it works fine. But I want to return BaseReponse<R>.

when an anonymous object captures a

var

reference from the adjacent scope in one of its methods, does it not see changes to the original reference (i.e., it captures its own reference to the value when the object is created)?

I do DI into my fragments like so:

class MyFragment : ... {
  @Inject lateinit var mViewModelFactory: ViewModelProvider.Factory
  private val mViewModel by lazy { 
    ViewModelProviders
      .of(requireActivity(), mViewModelFactory)
      .get(MyViewModel::class.java) // MyViewModel extends ViewModel
  }
}

Any idea how I might parametrize this into a base class to ideally get rid of ALL this boilerplate? I have

abstract class BaseFragment<VM: ViewModel>: ... {
  abstract var mViewModelFactory: ViewModelProvider.Factory
  private val mViewModel by lazy {
    ViewModelProviders
      .of(requireActivity(), mViewModelFactory)
      .get(?????)
  }
}

This wuold at least enable

class MyFragment<MyViewModel> {
  @Inject lateinit var mViewModelFactory: ViewModelProvider.Factory
}

But I’m stuck here. I thought about making a lookup table to map fragment classes to viewmodel classes, but would like to avoid that if possible. Thoughts? I doubt it can be done, but thought I’d ask here.

Is that behavior intended? I don't understand why my val fields are null here o.O It's a data class inside a data class

I'm trying to break up a large class by using class delegates (to avoid suppressing Detekt's TooLargeClass error), but finding it's not possible to access variables in the container class. How do folks handle something like this? class ContainerClass : X by ClassDelegate() { val something } class ClassDelegate { fun blah { // want to use something here... } }

Is there a way to add an annotation to a class defined in a separate library? Some kind of extension annotation? E.g. I have a class called

data class Foo()

in my network library, but I would like to add an annotation to it in my Android

app

module for use with my database.

What is the idiomatic Kotlin way to translate the following Swift snippet:

if let foo = someOptionalExpression, let bar = optionalExpression(foo) {

// work with foo AND bar

}

else {

// deal with nil/null case

}

There is a lib which provides following API:

suspend inline fun <reified T : Event> Client.addHandler(noinline action: suspend (T) -> Unit)

I have a handler interface

interface EventHandler<T : Event> {
    suspend fun handle(event: T)
}

And I have a list of handlers which is injected into my application:

val handlers: List<EventHandler<*>>

Each handler is defined as

MyHandler : EventHandler<MyEvent>

I need to somehow add these handlers to the client:

handlers.forEach { client.addHandler(it::handle) }

I'm getting

Cannot use 'Nothing' as reified type parameter

at the

.addHandler

What can I do to work around it?

Is there anyway to get the KClass that corresponds to a given functional type? Because Kotlin doesn’t do SAM conversion for Interfaces, I’m kinda unsure how to pass a functional type to another function that accepts a KClass. I’m primarily interested in using this to bind a singleton to a function type for the purposes of injection.

Something that has been bugging me for a while. What is the reasoning behind not allowing

latinit val

in Kotlin?

Hi guys ! What is the main purpose of

local function

in Kotlin? ( As far as I know, it is used for reuse common code inside a function )