This snippet of code is from the

Coursera

. I tried it on the Kotlin

REPL

. Any ideas why it is giving that error? Thanks! BTW, I get the same error for:

displayError()

!!!

I'm trying to setup my environment to contribute to Kotlin by following Yoshinori Isogai's talk of last KotlinConf, but I'm hitting a wall when running the command

ant -f update_dependencies.xml

. I get an error saying:

Java HotSpot(TM) 64-Bit Server VM warning: ignoring option MaxPermSize=512m; support was removed in 8.0
Buildfile: update_dependencies.xml does not exist!
Build failed

Any tips?

Everybody, I got a question about lambda and SAM conversion. The subject is Android here, but my question is actually Kotlin related so I post here. Why if I do use the "lambda version" to override the single interface method ( top in the image) I don't have to declare the "object: " explicitly, while if I try to explicitly override the single method, I have to? Thanks 😄

listOf() is by default immutable. mutableListOf() is mutable.

Although the last commit there is a year ago.

Guys how do i change function to make it get

T

from the

klass

?

fun <T> getProperty(klass: KClass<*>): T? {
        return properties.find { it::class == klass } as T?
    }

Right now it's working as

entity.getProperty<String>(String::class)

and i want

entity.getProperty(String::class)

can anyone please explain the following behavior

class A1(private val x: Int) {
    private val y: Int = 0
}

generates this code in Java

public final class A1 {
    private final int y;
    private final int x;

    public A1(int x) {
        this.x = x;
    }
}

while

class A2(private val x: Int) {
    private val y: Int
    init {
        y = 0
    }
}

generates

public final class A2 {
    private final int y;
    private final int x;

    public A2(int x) {
        this.x = x;
        this.y = 0;
    }
}

Why if init block

y=0

is in constructor of

A2

and not otherwise in case of

A1

?

I’ve recently checked out Kotlin Exposed, looks really cool, but feels rather immature at this point. What’s everyone’s favourite database library?

if the if missing a closing

)

?

Otherwise still doesn't compile because it's missing a real return.

actually

a ?: let {} ?: return b

seems okay a is final and always initialized to null so the let block is dead code

Still waiting for correct answer.

if a was not val/final then it could fall though and return

c

interesting overload

Which features attract you to use Kotlin?

functionThatTakesAVarargAsParameter(*fictionData )

?

Oh, the

arrayOf

exactly what i need, thanks

Is it possible to create a generic function extension? I've tried this but it doesn't work:

fun List<E>.getDifference(other: List<E>) = this.union(other) - this.intersect(other)

Guys, the IDE asks me to convert the comparison of `UByte`s into a range check. And I would gladly do it, but if I do

if (f.value in from..to && !c.isEmpty)

, then it doesn’t compile saying

Type interference failed

. Any other options?

fun notEmptyFieldInRange(from: UByte, to: UByte): Boolean {
        for ((f, c) in fields)
            if (f.value >= from && f.value <= to && !c.isEmpty)
                return true
        return false
    }

If I have a package and have functions declared in it (not any class besides package itself) - is it possible by using reflection to obtain list of those declared functions? I have tried to do something like this -

val o = object{}
val mm = o.javaClass.declaredMethods

but it doesn't return anything. is it possible at all? if so, would the function modifier affect this search (private, public, etc)?

How should the

Stateful by state()

part of this should be interpreted?

class MySuperCoolActivity : Activity(), Stateful by state()

and

state()

is a global function

How to handle ui in a multiplatform project. I mean can ui be in the shared/common module?

yeah that was what I was doing. But scratch files have a different ui and inline(only?) output console

I can’t seem to get scratch files to run currently.

Hi guys, I have a Kotlin module, packaged as a jar, that I use from a Java project I want to have a method that is visible from my Kotlin classes but not from the java project. From what I read on the doc (https://kotlinlang.org/docs/reference/visibility-modifiers.html) I thought that

internal

would do the trick but the internal function is visible from java, as : myInternalFunc$my_module_name. What am I missing ? 🤔 Mmmm read the doc a bit more and saw that internal is mapped to public in java with some name mangling. Do you know another way to do what I want to do ?

I am trying to debug some code. Some variables (newValue and tappedOperation here) are shown as a small circle with a "p" inside, and have several parameters (count, hash); while others (prevValue here) are shown with a different symbol. I feel like the latter shows the variable type (that's a double). But what about the others? They are arguments to a function call, but why are them so different here? THANKS ❤️

Hi, I'm trying to use the new gradle kotlin-dsl but my tests are not being run (although they are built). Is there an example project for this? The one generated with Intellij does not seem to run them. I'm using gradle 4.10.2, kotlin-dsl 1.3 and junit 5

Maybe a stupid question, but I've got quite a few companion objects, which need to be accessed from Java. Is there somehow a way to make all the functions is the companion objects JvmStatic by default, or, at least, put an annotation on the companion object or something? It would save me a ton of annotations.

Perhaps a silly question, how do people handle mocking data classes?

anyone got some good info about why kotlin went with its companion object concept over just having static?