Hi guys. I'm trying to write a DSL. Suppose I have this structure:

class A(val someObject : SomeObjectClass) {

    fun doSomethingWithSomeObject() {
        // TODO do something with someObject
    }
}

How would I achieve something like the following in Kotlin:

coolDSL(someObject) {

    doSomethingWithSomeObject {
        someObject.callSomeMethod()
    }

}

Thanks in advance.

Hello, I am trying to convert this line of Objective-C code to Kotlin´[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];´

Are questions regarding design patterns welcome? I have a tree of objects that I need to convert to a similar tree of other objects and the creation logic is quite complex. The object types are also in a hierarchy where only the leafs are non-abstract and can be instantiated. So right now I have a static factory method in each class that checks the necessary conditions and then returns the object or null (in the case of leaf types) or delegates the object creation to the right factory method of it's sub types (in the case of a non-leaf type). But I was thinking that it might be better to put all of that creation logic in a factory class. In particular, I think it will improve error handling since the nested nullable factory methods tend to swallow error reasons which makes debugging much harder. And since everything is in one place, there is less repetition of the necessary conditions for creating some object. But a big concern is that putting all the checks in the factory class would make it possible to create some class in an invalid state. I could of course also put the same checks into each constructor, but that repetition would make the whole thing pointless. What do you think? What are the pros/cons of one factory class vs nested factory methods vs checks in constructors that throw, and trying them all in order?

I did a compile to bytecode and decompile to java, and this appears to be the case:

public static final void main(@NotNull String[] args) {
  Intrinsics.checkParameterIsNotNull(args, "args");
  MyType bar$iv = new MyType();
  doSomething(bar$iv);
}

boneless?

Hello, you need to create activity in the menu / Mapa. Maps_activity is already created but located elsewhere. How can I do this? You can help me? I am a beginner. This is not working, it writes a mistake. Thank you Juraj override fun onOptionsItemSelected(item: MenuItem?): Boolean { when(item.itemId) { R.id.Mapa -> { startActivity(Intent(this, activity_maps::class.java)) return true } } return false } }

Hello, when will java 11/12 be supported ? i get this error message :

Hey, I'm working with android, when I try supply a 0xAARRGGBB number, with the alpha as FF, it requires me to cast to integer explicitly to apply it to an integer property, is there a way around that, or do I just keep casting to int?

how can I use .find with data class inserted into sealed class?

Can someone please explain why the second

println(f())

prints “Yes” instead of “No”?

fun main(args: Array<String>) {
    var (f, x) = g()
    println(f()) // Prints "yes"
    x = 1
    println(f()) // Prints "yes"
}

fun g(): Pair<() -> Char, Int> {
    var x = 0
    var f = fun(): Char { return if (x == 0) { println("yes"); 'Y' } else { println("no"); 'N' } }
    return f to x
}

How to make working this

val curSelectedItem = SimpleObjectProperty<ItemViewInstance>()

with something like this

when (curSelectedItem) { is ItemViewInstance.ItemModel }

? it works only if

curSelectedItem

isnt

SimpleObjectProperty

Hi. Is there any public schedule for version 1.3 availability? I've some coroutines presentations scheduled for November and was wondering if should already use the "non-experimental" model of 1.3.

in the last few months upgrading Kotlin with every version, our build times became slower and slower builds used to take around 2 minutes max, now we're lucky if we get a

mvn clean package

to run in 20-24 minutes even with the incremental option on, that first

mvn package

or running it from IntelliJ takes almost 30 minutes not sure if Kotlin compile times became much slower or if our code-base became exponentially bigger we have about 2k lines of Java code and 114k lines of Kotlin code, so not that enormous any suggestions on how to make it faster?

<plugin>
                <artifactId>kotlin-maven-plugin</artifactId>
                <groupId>org.jetbrains.kotlin</groupId>
                <version>${kotlin.version}</version>
                <configuration>
                    <jvmTarget>${java.version}</jvmTarget>
                    <compilerPlugins>
                        <plugin>jpa</plugin>
                    </compilerPlugins>
                    <pluginOptions>
                        <option>jpa:annotation=javax.persistence.MappedSuperclass</option>
                    </pluginOptions>
                </configuration>
                <executions>
                    <execution>
                        <id>compile</id>
                        <phase>generate-sources</phase>
                        <goals>
                            <goal>compile</goal>
                        </goals>
                        <configuration>
                            <sourceDirs>
                                <source>src/main/java</source>
                                <source>src/main/kotlin</source>
                                <source>src/main/resources</source>
                            </sourceDirs>
                        </configuration>
                    </execution>
                    <execution>
                        <id>test-compile</id>
                        <phase>process-test-sources</phase>
                        <goals>
                            <goal>test-compile</goal>
                        </goals>
                        <configuration>
                            <sourceDirs>
                                <source>src/test/java</source>
                                <source>src/test/kotlin</source>
                                <source>src/test/resources</source>
                            </sourceDirs>
                        </configuration>
                    </execution>
                </executions>
                <dependencies>
                    <dependency>
                        <groupId>org.jetbrains.kotlin</groupId>
                        <artifactId>kotlin-maven-noarg</artifactId>
                        <version>${kotlin.version}</version>
                    </dependency>
                </dependencies>
            </plugin>

is there any way to profile the build to see how much time each aspect is taking?

why the HTML DSL doesn't have the crossorigin attribute? how to overcome this limitation?

Unfortunately, for tests I need to call private function

fun read(bufferedReader: BufferedReader): List<String>

because when mocking

File

,

file.bufferedReader

gives

NullPointerException

Thank you, what about Exceptions handling, IMO is better that I’m not handling IOException here, but pass it further to the user. Do you agree @karelpeeters?

is there a nice way to get from a Set<String?> to a Set<String> then?

Getting this error which forces me to disable dce, why isn't dce ignoring the duplicate and going ahead?

I have a class which implement

MutableList<T>

with a delegate. The class doesn’t have other properties. How can I write a working

equals

method which includes the delegate. Can I access it somehow?

class WidgetListBuilder : MutableList<Widget> by mutableListOf() {

    inline fun <T : Widget> add(widget: T, init: T.() -> Unit): T {
        widget.apply(init)
        add(widget)
        return widget
    }

    override fun equals(other: Any?): Boolean {
        if (this === other) return true
        if (other !is WidgetListBuilder) return false
        // TODO handle list
        return true
    }

    override fun hashCode(): Int {
        return javaClass.hashCode()
    }
}

then what will happen if we do

open class Outer {
        val inner = Inner()
        open val foo = 3
        open inner class Inner {
            val innerFoo = foo // Accessing non-final property foo in constructor
        }
    }

?

is there a weak-reference ReadWriteProperty built-in to kotlin?

There's

fold

for things like that.

i think this is the repo: https://github.com/Kotlin/kotlin-koans-edu

Hi, this may be strange question. Where can I find

String#toString

implementation? I can see in Java

public String toString() {
        return this;
    }

but I can’t see this in Kotlin.

public class String : Comparable<String>, CharSequence {
    companion object {}
    
    /**
     * Returns a string obtained by concatenating this string with the string representation of the given [other] object.
     */
    public operator fun plus(other: Any?): String

    public override val length: Int

    public override fun get(index: Int): Char

    public override fun subSequence(startIndex: Int, endIndex: Int): CharSequence

    public override fun compareTo(other: String): Int
}

I can’t find extension function either…

Is there a reason we have binary functions instead of operators? Like

shr

,

shl

,

and

and

or

instead of

>>

,

<<

,

&

and

|

?

It seems a bit odd that I'm required to explicitly state the return type of

Nothing

in this case...

fun justThrowIt(): Nothing = throw IOException()

...while here, I'm not:

fun justLoop() { while (true) {} }

If I do add it, as in

fun justLoop(): Nothing { while (true) {} }

, the code does compile.

I have an abstract class

A

that has an abstract member property defined by an interface:

interface Tool {
  fun run(command: String): Boolean
}

abstract class A {
  abstract protected var tool: Tool
  fun execute(command: String) : Boolean {
    return tool.run(command)
  }
}

Then I have another class

B

that inherits from

A

and uses guice to inject the

tool

member property at startup.

class B {
  @Inject
  @Transient
  override protected var tool: Knife
}

where

Knife

is a concrete class implementing the interface

Tool

. Intellij is complaining to me:

Var property tye is `Knife`, which is not a type of overridden protected abstract var tool: Tool defined in com.myorg....

.