what is everyone's opinion on having private helper (extension) functions vs having nested helper functions

Does Kotlin/Native (say for iOS) creates - iOS binary or - the code that can be imported on XCode and then built into iOS binary or - both?

The

-

operator.

Hello guys. I have a question about generics. I have following code:

val properties = mutableListOf<Property>()

inline fun <reified T : Property> getProperty(): T? {
    return properties.filter { it::class == T::class }.firstOrNull() as T?
}

I don't like this

as T?

part, but if i remove it i will receive error:

Type inference failed. Required: T?, found: Property?

Am i doing something wrong?

I do have a lot of experience with Kotlin, but I'm afraid that I'll flood them with too much information that seems trivial for me

I got my team to use Kotlin by highlighting the inherent increase to code quality that using Kotlin brings. I also highlighted some OO design patterns that are built in constructs in the language itself. Plus I mentioned that it makes refactor work a lot easier. I think the fact that there is too many benefits to go over in a 30 min presentation is a convincing point in itself. The best of the best are using Kotlin.

Is it possible to reference a delegated property from Java? I would normally write this line in Kotlin:

var myString: String by SharedPrefsString(myPrefs)

but I wanna use my SharedPrefsString type in Java, if possible.

This message was deleted.

Just call

hashcode()

? Can you give an example?

I think this should work, but

Exception in thread "main" java.lang.NoSuchMethodException: com.potrero.Application.main([Ljava.lang.String;)
	at java.base/java.lang.Class.getDeclaredMethod(Class.java:2476)
	at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:47)
	at org.springframework.boot.loader.Launcher.launch(Launcher.java:87)
	at org.springframework.boot.loader.Launcher.launch(Launcher.java:50)
	at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:51)

package com.potrero

import org.apache.logging.log4j.LogManager
import org.springframework.beans.factory.getBeanProvider
import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.info.BuildProperties
import org.springframework.boot.runApplication

@SpringBootApplication
open class Application

fun main(args: Array<String>) {
    val ctx = runApplication<Application>(*args)
    ctx.getBeanProvider<BuildProperties>().ifAvailable {
        LogManager.getLogger(Application::class.java).info("Starting {}", it.artifact)
    }
}

shouldn’t this kotlin class work to start spring boot?

I get a 403 here

Any suggestions / guidance on how I might optimise this? The arrays contain ~600 elements and this is executed every 500ms to formulate this string which then gets written to a file. Cpu is averaging ~30%.

fun SamplingEvent.DataEvent.SensorArrayValuesEvent.toSensorDataString(): String {
    var segment = ""
    for (i in 0..(sensorCount - 1)) {
        segment += "$timestampNanos,${sensorType[i]},${values0[i]},${values1[i]},${values2[i]},${values3[i]},${values4[i]},${values5[i]}\n"
    }
    return segment.dropLast(1)
}

My first instinct is to lift this out of extension function and use/reuse StringBuilder (with sufficient initial buffer) ?

This prints

first=1 (int)

but I thought kotlin has no implicit conversions.

This decompiles as

List listOfDouble = CollectionsKt.listOf(1.0D);
      if (listOfDouble == null) {
         throw new TypeCastException("null cannot be cast to non-null type kotlin.collections.List<kotlin.Int>");
      } else {
         int first = ((Number)listOfDouble.get(0)).intValue();
         System.out.println("first=" + first + " (" + Integer.TYPE.getName() + ')');
      }

A lot of the embedded examples here : https://blog.jetbrains.com/kotlin/2018/04/embedding-kotlin-playground/ no longer seem to work 😞

Does variable initialization out of

init{}

occur after init and if so, is it a good practice if order matters to include it in

init{}

? i.e.,

class Logger(val logFile: Path)
{

    val writer = Files.newBufferedWriter(logFile)
    
    init {
        if(!Files.exists(logFile))
        {
            Files.createFile(logFile)
        }
    }
}

also is there a

.field

equivalent in Kotlin for constructors? I can't seem to find one, and it is really annoying to manually create the property definition...

Option also allows for much more control. Nullable types are nice but really don't offer anything in itself. Option implements typeclasses like Functor (enables .map), Monad (enables flatMap/bind), and lots more. This is functionality that nullable types can't provide and by using those typeclasses programs tend to become a lot simpler imo

Q: Looking for what I expected Collection.singleOrNull() would do but doesn't, i.e. return single if 1 element, null if empty and throw if > 1 i.e. equivient to when( size ) { 0 -> null ; 1 -> first() ; 2 -> throw } Is there such a beast ? Its easy to write but maybe Im looking for the wrong words

guys when i upgrate gradle plugin from 1.3.0 to 1.3.11, for some reason, dependencies in a module with API are not visible in another module that includes the previous one. any1 experimenting stuff like this ?

Is there a way to specify that I want to use boxed version of

val

? I use DI framework and it finds primitive

boolean

here:

class MyPresenter @Inject constructor(val field: Boolean)

and fails to generate injector. One way is to use

val field: java.lang.Boolean

, but it feels a bit dirty and generates a warning

I had this Java code:

@Bean
    @ConditionalOnProperty( prefix = "proxy", name = "enabled", havingValue = "true")
    public RestTemplateCustomizer restTemplateCustomizer() {
        return restTemplate -> {
            var proxy = new HttpHost(host, port, scheme);
            var httpClient = HttpClientBuilder.create().setRoutePlanner(new DefaultProxyRoutePlanner(proxy)).build();
            restTemplate.setRequestFactory( new HttpComponentsClientHttpRequestFactory(httpClient));
        };
    }

where RestTemplateCustomizer is a functional interface. But I have trouble writing this in Kotlin

What is the better way to handle system path (

/path/to/file

), than store it as a

String

? Better way to split it later by directories (

path

,

to

,

file

)?

Anyone know why I might be getting

Cannot access class 'kotlinx.serialization.KSerialLoader'. Check your module classpath for missing or conflicting dependencies

? I’ve followed the directions in the kotlinx readme.

How do I get clipboard access (read/write) on Kotlin, not Android, not AWT, not JavaFX, pure Kotlin for OS usage? I searched everywhere, the best answer so far has been to force users to install xclip, and call it from Runtime(), which is not a great solution.

Is there any particular reason that

class ReactMap : MutableMap<Long, MutableList<EmoteData>> by (mutableMapOf<Long, MutableList<EmoteData>>()
    .withDefault { mutableListOf<EmoteData>() })

compiles fine, and

class ReactMap : MutableMap<Long, MutableList<EmoteData>> by mutableMapOf()

compiles fine, but

class ReactMap : MutableMap<Long, MutableList<EmoteData>> by (mutableMapOf().withDefault { mutableListOf() })

doesn't? Is it a bug in the compiler, or is it intentional?

Hey If I have a parameter defined as

test: KClass<Any>

how can I fix the problem that when for example passing in

MyClass::class

the type missmatch error?

is there any way to inherit super class default constructor values?

open class A(val a: String, val b: String = "hello")

class B(a: String, b: String, c: String) : A(a, b) {

}

in this scenario would it be possible to have

b

arg in class

B

have default value

"hello"

while being DRY?

also, any reason an arg of type

Runnable

can be called with

() -> Unit

but when the type is

Runnable...

?,

() -> Unit

cannot be called?