Any alternative suggestion (more kotlin idiom/functional approach) to extract the following string? from:

<deeplink scheme>://jobs?category_id=asdf&employment_type=FULLTIME

into a query parameter (what I can think of atm was map):

mapOf(
   "category_id" to "asdf",
   "employment_type" to "FULLTIME"
)

my code attempts in 🧵

Hey guys!

var millis = 123L
var i = 0
buildList<Pair<TimeUnit, Long>> {
  add(Year to (millis / MillisInYear))
  millis -= (get(i++).second * MillisInYear)
  add(Month to (millis / MillisInMonth))
  millis -= (get(i++).second * MillisInMonth)
  add(Day to (millis / MillisInDay))
  millis -= (get(i++).second * MillisInDay)
  add(Hour to (millis / MillisInHour))
  millis -= (get(i++).second * MillisInHour)
  add(Minute to (millis / MillisInMinute))
  millis -= (get(i++).second * MillisInMinute)
  add(Second to (millis / 1_000))
  millis -= (get(i++).second * 1_000)
  add(Millisecond to millis)
}

This code is used to make a timer/counter (picture) However, it's very ugly as it is. How can I enhance this?

Is there a way to simplify this logic?

var qtdTotal = 0.0f
            val partition = response?.partition { it.uidCaracteristica != 0 }
            val uidGroup = partition?.first?.groupBy { it.produto }?.toMutableMap() ?: mutableMapOf()
            uidGroup[0] = partition?.second ?: listOf()
            uidGroup.forEach { (key, uidsList) ->
                if (key == 0) {
                    uidsList.forEach { stk ->
                        addRow(
                            stk.description ?: "", "", "", "",
                            extraInfo = listOf(
                                stk.produto.toString(),
                                stk.description ?: "",
                                stk.codbarras ?: "",
                                stk.referencia ?: ""
                            )
                        )
                        qtdTotal += stk.stock ?: 0.0f
                    }
                } else {
                    val caracteristicas = uidsList.map {
                            ReportsDataset.Row(
                                it.caracteristica ?: "",
                                it.stkmin?.toString() ?: "",
                                it.stkmax?.toString() ?: "",
                                it.stock?.toString() ?: "",
                                extraInfo = listOf(it.uidCaracteristica?.toString() ?: "")
                            )
                        }
                    val stk = uidsList.first()
                    addRow(
                        stk.description ?: "", "", "", "",
                        extraRows = caracteristicas,
                        extraInfo = listOf(
                            stk.produto.toString(),
                            stk.description ?: "",
                            stk.codbarras ?: "",
                            stk.referencia ?: ""
                        )
                    )
                    qtdTotal += stk.stock ?: 0.0f
                }
            }

Does the UseCase always necessary to have a

CoroutineDispatcher

and returns

Flow<T>

or

suspend

(return

T

) is enough?

abstract class FlowUseCase<out T, in Params> constructor(
    private val threadExecutor: CoroutineDispatcher
) {
    protected abstract fun execute(params: Params? = null): Flow<T>
    open operator fun invoke(params: Params? = null): Flow<T> =
        execute(params).flowOn(threadExecutor)
}

What implementation did you folks use, would love to know the pros n cons

This message was deleted.

How can I evaluate both of these in a single operator chain?

val adminOf = user.roles
    .filter { it.isAdmin() }
    .map { it.entityId to it.entity }
    .toMap()
val serviceProviderOf = user.roles
    .filter { it.isServiceProvider() }
    .map { it.entityId to it.entity }
    .toMap()

Can any1 help me understand why the built-in type inference for map is not working

I'm torn … do you extract the

return

even if some branches don't return anything? I think I might like the version with multiple return statements better in this case…

return if (someExpr) {
  doSomeStuff()
  someThing
} else if (otherExpr) {
  doOtherStuff()
  otherThing
} else {
  throw RuntimeException("uh oh")
}

Any recommendation or preferences for following snippet?

preconditions

or

throw

for this case, maybe any references?

1️⃣

suspend fun updatePushToken(newPushToken: String): Result<String> = invoke {
    require(newPushToken.isNotEmpty()) { "Push token is required to not empty" }

    kotlin.runCatching { repository.agentUpdatePushToken(newPushToken = newPushToken) }
}

or 2️⃣

suspend fun updatePushToken(newPushToken: String): Result<String> = invoke {
        
        if (newPushToken.isEmpty()) {
            throw IllegalArgumentException("Push token is required to not empty")
        }
        
        kotlin.runCatching { repository.agentUpdatePushToken(newPushToken = newPushToken) }
    }

I’ve got a

data class Thing(val x: Int, val y: Int, val ignoreMe: String)

which I want to put in a set to perform set operations, but ignore certain fields for the purpose of set comparison. i.e. only considering a subset of fields for equality comparisons.

val x = setOf(Thing(5, 5, "Hello"), Thing(10, 6, "Goodbye"), Thing(100, 3, "Zzzz"))
val y = setOf(Thing(5, 5, "Baz"), Thing(10, 6, "Goodbye"))
val result = x.minus(y)
 -> result = setOf(Thing(100, 3, "Zzzz")) // because Thing(5, 5, "Hello") is considered equal to Thing(5, 5, "Baz")

In reality the data classes are a bit richer, about 6 fields. I thought I could build a sorted set with a custom comparator, but that requires implementing a sorting on the data classes when I only really want a custom equality for that set. I only want this custom equality behaviour in one context, so it’s not appropriate to actually re-implement

equals

etc on the data classes directly. Any ideas about if there’s a simple way to achieve this? (edit - found a nice idea on stack overflow - just wrap the objects in a special purpose class)

Does anyone have any tips as to how I can improve this code? Something about it seems messy but I can't pinpoint what it is. I created my own

FileHelperUtilities

class in Kotlin to help with: • Saving a Bitmap as PNG/JPG • Opening an image from a URI with an

Intent

Code:

bject FileHelperUtilities {
    fun saveBitmapAsImage(compressionOutputQuality: Int, compressionFormat: Bitmap.CompressFormat, onTaskFinished: (OutputCode, File) -> Unit, context: Context) {
        // Thanks to <https://stackoverflow.com/users/3571603/javatar> on StackOverflow - quite a bit of the code is based off of their solution

        var outputCode = OutputCode.SUCCESS
        val pathData = "image/jpeg"
        val outputName = if (compressionFormat == Bitmap.CompressFormat.PNG) "$projectTitle.png" else "$projectTitle.jpg"

        val environmentRoot = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DCIM).toString()
        val directory = File(environmentRoot)

        directory.mkdirs()

        val file = File(directory, outputName)

        try {
            val outputStream = FileOutputStream(file)
            val bitmapToCompress =  outerCanvasInstance.fragmentHost.drawToBitmap()
            bitmapToCompress.compress(compressionFormat, compressionOutputQuality, outputStream)
            outputStream.close()
        } catch (exception: Exception) {
            outputCode = OutputCode.FAILURE
        } finally {
            onTaskFinished(outputCode, file)
        }

        MediaScannerConnection.scanFile(context, arrayOf(file.path), arrayOf(pathData), null)
    }

    fun openImageFromUri(uri: Uri, onTaskFinished: (OutputCode) -> Unit, context: Context) {
        var outputCode = OutputCode.SUCCESS
        val intentAction = Intent.ACTION_VIEW
        val type = "image/*"

        val intent = Intent()
        intent.action = intentAction
        intent.setDataAndType(uri, type)

        try {
            context.startActivity(intent)
        } catch (exception: Exception) {
            outputCode = OutputCode.FAILURE
        } finally {
            onTaskFinished(outputCode)
        }
    }
}

Here it is in use:

package com.realtomjoney.pyxlmoose.customviews.pixelgridview

import android.graphics.Bitmap
import android.net.Uri
import com.realtomjoney.pyxlmoose.activities.canvas.projectTitle
import com.realtomjoney.pyxlmoose.enums.OutputCode
import com.realtomjoney.pyxlmoose.extensions.SnackbarDuration
import com.realtomjoney.pyxlmoose.extensions.showSnackbar
import com.realtomjoney.pyxlmoose.extensions.showSnackbarWithAction
import com.realtomjoney.pyxlmoose.utility.FileHelperUtilities
import java.io.File

lateinit var file: File

fun PixelGridView.extendedSaveAsPNG() {
   FileHelperUtilities.saveBitmapAsImage(90, Bitmap.CompressFormat.PNG, { outputCode, _file ->
       if (outputCode == OutputCode.SUCCESS) {
           file = _file

           showSnackbarWithAction("Successfully saved $projectTitle as PNG", SnackbarDuration.MEDIUM, "View") {
               FileHelperUtilities.openImageFromUri(Uri.fromFile(file), { outputCode ->
                   if (outputCode == OutputCode.FAILURE) {
                       showSnackbar("Error trying to view file", SnackbarDuration.DEFAULT)
                   }
               }, context)
           }
       } else {
           showSnackbar("Error saving $projectTitle as PNG", SnackbarDuration.DEFAULT)
       }
    }, context)
}

/**
 * usage: val regex by "foo".lazyRegex(RegexOption.IGNORE_CASE)
 * instead of:
 * val regex by lazy { "foo".toRegex(RegexOption.IGNORE_CASE) }
 * or:
 * val regex = "foo".toRegex(RegexOption.IGNORE_CASE)
 */
fun String.lazyRegex(option: RegexOption? = null): Lazy<Regex> =
    lazy {
        if (option == null)
            toRegex()
        else
            toRegex(option)
    }

So here, if you already have a bunch of properties like:

val regex = "foo".toRegex()

you can very easily convert to:

val regex by "foo".lazyRegex()

How good is this?

import java.util.UUID

enum class Color {
    RED, ORANGE, YELLOW, GREEN, BLUE, PURPLE, TRANSPARENT
}

interface Shape {
    val name: String
    val uuid: UUID
        get() = UUID.randomUUID()
    val width: Int
    val height: Int
    val fillColor: Color
    val strokeThickness: Int
    val strokeColor: Color
    fun draw()
    fun erase()
}

class Square(
    override val width: Int,
    override val height: Int,
    override val fillColor: Color,
    override val strokeThickness: Int,
    override val strokeColor: Color
    ) : Shape {
    init {
        if (width != height) {
            throw IllegalArgumentException("Length must be equal to width.")
        }
    }

    override val name = "Square"

    override fun draw() {
        println("$name has been drawn.")
    }

    override fun erase() {
        println("$name has been erased.")
    }
}

class Rectangle(
    override val width: Int,
    override val height: Int,
    override val fillColor: Color,
    override val strokeThickness: Int,
    override val strokeColor: Color
    ) : Shape {
    override val name = "Rectangle"

    override fun draw() {
        println("$name has been drawn.")
    }

    override fun erase() {
        println("$name has been erased.")
    }
}

class Canvas(
    private val width: Int,
    private val height: Int,
    private val shapeData: MutableList<Shape>
    ) {
    init {
        for (shape in shapeData) {
            if (shape.width > this.width || shape.height > this.height) {
                throw IllegalArgumentException("Shape of ${shape.uuid} is too large.")
            }
        }
    }

    fun eraseContents() {
        for (shape in shapeData) {
            shape.erase()
        }
    }

    fun drawContents() {
        for (shape in shapeData) {
            shape.draw()
        }
    }
}

Hello peps, I have a state class like below:

data class ViewState(
    var startDateTime: LocalDateTime? = null,
    var endDateTime: LocalDateTime? = null,
    var totalBreakDuration: Duration? = null,
    var onEditClick: () -> Unit = {}
) {
    fun totalDuration() = startDateTime?.let { startDateTime ->
        endDateTime?.let { endDateTime ->
            Duration.between(startDateTime, endDateTime)
        }
    }

    fun workDuration() = totalDuration()?.minus(totalBreakDuration!!)
}

I have stateImplementation like Below:

state.startDateTime?.let {
                    ViewItemState(
                        label = "label",
                        value = it.format(ISO_LOCAL_DATE)
                    )
                }?.let(binding.dateItem::setupWithState)
-----------------------------------------------------------------
                state.startDateTime?.let {
                    ViewItemState(
                        label = "label"
                        value = it.format(ISO_LOCAL_TIME)
                    )
                }?.let(binding.startTimeItem::setupWithState)
-----------------------------------------------------------------------------
                state.endDateTime?.let {
                    ViewItemState(
                        label = "label",
                        value = it.format(ISO_LOCAL_TIME)
                    )
                }?.let(binding.endTimeItem::setupWithState)
-----------------------------------------------------------------------------
                state.totalDuration()?.let { DurationFormat().format(it) }?.let {
                    ViewItemState(
                        label = "label",
                        value = it
                    )
                }?.let(binding.totalTimeItem::setupWithState)
-----------------------------------------------------------------------------
                state.totalBreakDuration?.let { DurationFormat().format(it) }?.let {
                    ViewItemState(
                        label = "label,
                        value = it
                    )
                }?.let(binding.totalBreakTimeItem::setupWithState)
-----------------------------------------------------------------------------
                state.workDuration()?.let { DurationFormat().format(it) }?.let {
                    ViewItemState(
                        label = "label",
                        value = it
                    )
                }?.let(binding.workTimeItem::setupWithState)

This method works nicely if a person has a middle name, but if they don't. Then it print

[FIRST]..[LAST]

Notice the two dots are supposed to show that there are two spaces. What's a convenient way of only having a single space?

private fun Person.prettyPrint() =
        "${this.data.firstName} ${this.data.middleName} ${this.data.lastName}"

I am updating Effective Kotlin Item 33: Consider factory functions instead of secondary constructors. I changed that completely, may I ask for a feedback? https://docs.google.com/document/d/1jN6gltGAN6DMr-_sKoRFStVsaymp-V8ajYvDeVztKOo/edit?usp=sharing

Hello, I have a use case where I have 2 separate files witch expose public top-level functions (extension functions for mapping objects) calling private helper functions inside them. The issue is that some of those private functions duplicate and I would like to reuse them rather than copy-paste them and don't want to make them public so that they're visible from everywhere. The first thing that comes to my mind is OOP approach where I encapsulate those private functions to an abstract class, implement public extensions inside singleton objects inheriting this abstract class, and then import those extensions statically when used to work on them as on top-level functions. Example: SampleModifications.kt:

abstract class SampleModifications {
    protected fun helper1(...) [...]

    protected fun SampleField.helper2(...) [...]
}

helpers usage: SampleMapper.kt

object SampleMapper : SampleModifications() {
    fun Sample.toSomethingElse() = [...] // calling helper1 from SampleModifications inside

    [...]
}

extensions usage:

import [...].SampleMapper.toSomethingElse

[...]

sampleRepository.findByIdOrNull(id)?.toSomethingElse()

This works fine and does what I want but declaring abstract classes for such use case seems like overkill for me so wondering if I could achieve the same cleaner or maybe more idiomatic, how would you approach it?

Goal: lazy map (where we only need the getter) supporting multithreaded access. Is there a better way?

val getValuesForKey: (String) -> Set<String> =
    object : (String) -> Set<String> {
        val map = mutableMapOf<String, Set<String>>()

        override fun invoke(key: String): Set<String> =
            synchronized(this) {
                map.getOrPut(key) {
                    calculateValuesForKey(key)
                }
            }
    }

Hey folks! Posting this message here as well, I think may be the better channel for the purpose of my message 😄

Hello people!

I am new to Kotlin 🔥

I do have a Golang background, and I have to admit that I am enjoying it so far!

I’d love if some of you would give me some feedback about this project I am doing just as a server for practicing Kotlin 🙂

Let me know if you spot any bad practice in the source code, happy to receive some constructive feedback!

Hey guys! I'd like to discuss the following syntaxes:

fun insertAll(uses: Iterable<Use>) {
  uses.forEach { insert(it) }
  uses.forEach(::insert)
}

What do you think about both approaches?

Could someone review our BaseViewModel on coroutines? It delegates all context handling to special object uiCaller, which enables composition of ViewModel logic

Hey Guys, I am working in ktor api response. I want to handle api response. So i read from some medium post. I tried some code. Can you suggest me if there is any better approach then this?

package com.example.kotlinmultiplatformsharedmodule
 
 sealed class ApiResponse<out T : Any> {
 
     data class Success<out T : Any>(
         val data: T?
     ) : ApiResponse<T>()
 
     data class Error(
         val exception: Throwable? = null,
         val responseCode: Int = -1,
         val errorResponse: ErrorResponse? = null
     ) : ApiResponse<Nothing>()
 
     fun handleResult(onSuccess: ((responseData: T?) -> Unit)?,onError: ((error: Error) -> Unit)?) {
         when (this) {
             is Success -> {
                 onSuccess?.invoke(this.data)
             }
             is Error -> {
                 onError?.invoke(this)
             }
         }
     }
 }
 
 data class ErrorResponse(
     val errorCode: Int,
     val errorMessage: String
 )

Hi guys, how can I refactor that code?

val productShopInfoItems = productListItemMapper.toShopInfoItems(it.snapshot)

state.productList.value?.forEach { product ->
    productShopInfoItems.forEach {  shop ->
        if(product.productId == shop.productId){
            product.shopInfoItemList += shop
        }
    }
}

product is

data class ProductItem(
    val productId: String = "",
    val productName: String = "",
    var shopInfoItemList: List<ShopInfoResponseItem> = emptyList<ShopInfoResponseItem>()
)

I'm modifying some code that looks like this (middle 8 lines omitted):

dialpad_0_holder.setOnClickListener { dialpadPressed('0', it) }
dialpad_9_holder.setOnClickListener { dialpadPressed('9', it) }

If the flag

tremor

is

true

, I would like to call

setOnLongClickListener

instead of

setOnClickListener

. Is it possible to do something like this?

val f = if (tremor) RelativeLayout.onLongClickListener else RelativeLayout.onClickListener
dialpad_0_holder.f { dialpadPressed('0', it) }
dialpad_9_holder.f { dialpadPressed('9', it) }

Which is better and why? 1️⃣ This is broken

return binding.myField.getWidth() != 0 ? binding.myField.getWidth() : binding.otherField.getWidth()

2️⃣

return binding.myField.getWidth().let {
    if (it != 0) it else binding.otherField.getWidth()
}

3️⃣ by @Luke

return if (binding.myField.getWidth() != 0) binding.myField.getWidth() else binding.otherField.getWidth()

Good Morning guys, What is the best approach to find three items in single list. I tried some code and working fine. I want to know is there any better approach for this

val completeEvent = events?.lastOrNull { events -> events.status == "complete" }
val activeEvent = events?.find { events -> events.status == "active" }
val futureEvent = events?.firstOrNull { events -> events.status == "future" }

ApiResponse

"Events": [{
			"title": "Test 1",
			"status": "complete"
		}, {
			"title": "Test 2",
			"status": "complete"
		}, {
			"title": "Test 3",
			"status": "complete",
		}, {
			"title": "Test 4",
			"status": "complete"
		}, {
			"title": "Test 5",
			"status": "complete"
		}, {
			"title": "Test 6",
			"status": "active"
		}, {
			"title": "Test 7",
			"status": "future"
		}, {
			"title": "Test 8",
			"status": "future"
		}]

Hi all, is it possible to rewrite this in a better way?

fun SomeEnum.getImageRes(
    param: SomeOtherEnum
): Int {
    return when (param) {
        SomeOtherEnum.OtherEnumA -> {
            when (this) {
                SomeEnum.EnumA -> R.drawable.res1_a
                SomeEnum.EnumB -> R.drawable.res1_b
            }
        }
        SomeOtherEnum.OtherEnumB -> {
            when (this) {
                SomeEnum.EnumA -> R.drawable.res2_a
                SomeEnum.EnumB -> R.drawable.res2_b
            }
        }
    }
}

Would anyone have an opinion if these 2 functions combining

use

and

with

should be added to the standard library:

inline fun <T : AutoCloseable?, R> T.useWith(block: T.() -> R): R = use(block)
inline fun <T : Closeable?, R> T.useWith(block: T.() -> R): R = use(block)

Looking for feedback on naming and implementation. If all items transform to the same value, then that value is returned, otherwise null

fun <T, R> Iterable<T>.singleOrNullBy(transform: (T) -> R): R? {
    if (this is Collection && this.isEmpty()) return null
    return asSequence()
        .map(transform)
        .zipWithNext()
        .map { (a, b) -> if (a == b) a else null } // important we don't use mapNotNull here
        .distinct()
        .singleOrNull()
}

fun <T> Iterable<T>.splitByIndex(index: Int): Pair<List<T>, List<T>> {
    if (index <= 0) {
        return emptyList<T>() to this.toList()
    }
    val iterator = this.iterator()
    val firstList = mutableListOf<T>()
    val secondList = mutableListOf<T>()
    var activeList = firstList
    while (iterator.hasNext()) {
        if (activeList.size == index) {
            activeList = secondList
        }
        activeList.add(iterator.next())
    }
    return firstList to secondList
}

Is it okay to check the

size

each time or better to maintain a local

Int

count?