Hi everyone 👍

Is there anything analogues to Swifts if let else paradigm in Kotlin?

or should we just use normal if/else blocks

Im not all that familiar with swift, but I feel like you could use an elvis

thanks

companion object, when declared inside of a class, is one instance per class instance?

how to access class instance's

this

from companion object?

No, there exists only a single companion instance per class, you can use it like this:

MyClass.companionFunction()

. What you're looking for is nested classes.

Hi again, another question about IDEA, gradle and annotation processing. Can I somehow specify in my desktop project gradle files to run the annotation processing tasks when the project is built in IDEA? Right now I'm in a similar situation like in this example: https://github.com/JetBrains/kotlin-examples/tree/master/gradle/kotlin-dagger Building the project succeeds fine from the command line, but build from IDEA complains about Dagger generated classes not being found. If I select the kaptKotlin task from the Gradle view on the right sidebar and check Execute before build it works fine. I was wondering if I could add something to my build files to automate this.

Is it possible to have a data class that extend a sealed class with own fields? e.g.

sealed class Vehicle {
    var color: String = ""
    var make: String = ""
}

data class SportsCar(val color: String, val make: String, val model: String): Vehicle

You could make

color

and

make

open

I don't think data classes can extend anything? In general,

equals

can't be correctly implemented with inheritance, so they just disallowed it completely.

if you care about interop, is it better to leave public-static-final-field-classes as java? example:

public class HttpHeader {
    public static final String ACCEPT = "Accept";
    public static final String ACCEPT_CHARSET = "Accept-Charset";
    public static final String ACCEPT_ENCODING = "Accept-Encoding";
}

seems like it's just more work to do it in kotlin, unless i'm missing something

@tipsy I wouldn't say so.

@file:JvmName("HttpHeader")

const val ACCEPT = "Accept"
const val ACCEPT_CHARSET = "Accept-Charset"
const val ACCEPT_ENCODING = "Accept-Encoding"

Can be used from Java as

HttpHeader.ACCEPT

and can be used from Kotlin as

ACCEPT

should be

const

otherwise 👍

penny-pinching characters helps no one

@jw Indeed, I like that better as they could then be used in annotations. I'll fix that. Can `@JvmField`s be used in annotations as well?

@jw ah, thanks

that's perfect

If I have a

Map<String, List<String>>

, how do I 'unwrap' that inner list to a

Map<String, String>

, wherein each element of the inner list is paired to the correct key?

What do you mean by the correct key? You can't have duplicate keys in a map.

Are you trying to create a

List<Map<String, String>>

?

or rather

List<Pair<String, String>>

I think the correct answer is write a test for the function in question

@trevjones That's what I meant, not list of maps 🙂