kotlinlang #codereview

@Andreas Sinz Okey, what would you suggest as a good workaround since I do work in a mixed java-kotlin project and have a lot of interfaces in java that I have to implement in kotlin, and this problem occurs from time to time.

voddan

04/01/2017, 1:53 PM

What's the deal with

KFunction1<@ParameterName(name = "ctx") RoutingContext, Unit>

? Is it better than

(ctx: RoutingContext) -> Unit

vinicius.rob.cunha

05/05/2017, 2:16 PM

Hello, has any way to improve this conditional?

read.cutOn != meterCut && (meter.cutDate != null || readDate.after(meter.cutDate))

Daniel

05/08/2017, 11:09 PM

Suppose I want to get the lowest property of an object in an array of said objects, might there be a better way than:

source.minBy { it.startX }?.startX ?: 0

Maybe a way to get the value of the property directly from the collection instead the object which it belongs to?

cleiter

05/09/2017, 8:38 AM

@christophsturm something like

val (a, b) = if (true) Pair("a", "b") else Pair(null, null)

👍 1

michaelsims

05/10/2017, 1:54 PM

I only see

var num

, no

var buf

michaelsims

05/10/2017, 1:54 PM

while (true) {
    val num = fi.read(buf).takeIf { it > 0 } ?: break
    fo.write(buf, 0, num)
}

👍 2

pguardiola

05/28/2017, 8:12 AM

If I define it using the concrete type

String

doesn’t complaint don’t know why but it works ¯\_(ツ)_/¯ thanks @anstaendig 👍

tipsy

06/03/2017, 12:45 PM

i know this is probably too much to ask, but i'm looking into porting my java-project to kotlin. i've done the port, and it seems to be working, but it would be great if someone who knows more kotlin than i do could scroll through and see if things are okay: https://github.com/tipsy/javalin/pull/11

dh44t

06/03/2017, 8:11 PM

I'll have a look, no promises

jlleitschuh

06/05/2017, 9:11 PM

If I have a kotlin interface like this:

interface IncomingJsonMessageHandler {
    operator fun invoke(methodName: String, arg: String): String
}

Is this really the only good way to declare the constructor so that I can use it both for DI and as a lambda in tests is to do this goofyness:

class IncomingRPCHandler
@Inject constructor(
    private val connectionProvider: ConnectionProvider,
    private val incomingJsonMessageHandler: IncomingJsonMessageHandler) {

    internal constructor(
        connectionProvider: ConnectionProvider,
        incomingJsonMessageHandler: (String, String) -> String) :
        this(connectionProvider, object : IncomingJsonMessageHandler {
            override fun invoke(methodName: String, arg: String): String = incomingJsonMessageHandler(methodName, arg)
        })

x80486

06/18/2017, 2:37 AM

Hackers...do you have a better way to write this piece of code?

import org.jetbrains.kotlin.com.intellij.util.TimeoutUtil

val formatter = DateTimeFormatter.ofPattern("yyyyMMddHHmmssSSS")
val regex = Regex("^V\\d+__.*\\.js\$")
File("src/main/resources/db/migration").walk()
    .filterNot { it.isDirectory or it.name.matches(regex) }
    .forEach {
      val timestamp = ZonedDateTime.now(ZoneOffset.UTC).format(formatter)
      it.renameTo(File("${it.parent}${File.separatorChar}V${timestamp}__${it.name}"))
      TimeoutUtil.sleep(100) // Wait for a moment to avoid prefix conflicts when renaming multiple files in a batch
    }

trubesv

09/16/2017, 12:11 PM

Hey guys, I'm making this really simple app in order to learn Kotlin and its best practices: https://github.com/trubesv/Kotlist Please do correct me if I'm using things wrongly, and don't hesitate to show me how to write some parts better! :kotlin:

Eugen Martynov

10/10/2017, 5:53 PM

Would you expect to find extension method in another class if you own code of the class?

alchzh

11/20/2017, 2:26 PM

Can someone review my code? Just started learning Kotlin this morning, so decided to port over some existing code... https://github.com/acz13/anagrams/tree/kotlin-rough/kotlin (x-post from #getting-started )

menegatti

11/21/2017, 3:13 PM

short explanation: you map every assignee to its goal, and then you flatten that to get what you want

Shawn

11/23/2017, 7:42 PM

@ecampolo if you want your code reviewed, you gotta put up your attempt to solve the problem

jkbbwr

12/15/2017, 8:11 PM

!!

is a code smell. B) Why crush it down further.

elect

12/15/2017, 10:13 PM

srcConnections.getOrPut(src, ::arrayListOf) += c

Dave Leeds

01/09/2018, 6:50 PM

@chi It’s a bit of a different approach, but something like this might work well:

private enum class NestingCharacters(val open: String, val close: String) {
    BRACE("{", "}"),
    PAREN("(", ")"),
    BRACKET("[", "]");

    fun apply(char: String, stack: Stack<String>) {
        when (char) {
            open  -> stack.push(char)
            close -> {
                val top = stack.peek()
                if (stack.isStackEmpty()) throw SyntaxErrorTwoException(char)
                if (top == open) stack.pop() else throw SyntaxErrorThreeException(top, char)
            }
        }
    }
}

fun linter2(line: String): Boolean {
    with(Stack<String>()) {
        line.split("").forEach { char ->
            NestingCharacters.values().forEach { it.apply(char, this) }
        }
        
        if (isNotEmpty()) throw SyntaxErrorOneException(peek())
    }
    return true
}

✅ 2

roberto.guerra

01/11/2018, 6:22 PM

Java doesn’t support multiple inheritance

Shawn

01/19/2018, 5:00 PM

if (!existCell.isEmpty()) {
  cell = when(existCell[existCell.size - 1]) {
    1 -> 9
    3 -> 7
    7 -> 3
    9 -> 1
    else -> 0  // or some default value
  }
}

👍 1

rocketraman

01/22/2018, 2:56 PM

@Ayden When you have so many `if`s like that, it is often wise to consider a state machine approach instead.

oday

01/23/2018, 8:13 AM

is there a process here about how much code to show, where to show it? can it be an Android app written in Kotlin?

Ayden

01/23/2018, 3:25 PM

if (
                    player1List.containsAll(listOf(1, 3, 7)) ||
                    player1List.containsAll(listOf(1, 3, 9)) ||
                    player1List.containsAll(listOf(1, 7, 9)) ||
                    player1List.containsAll(listOf(1, 3, 8))
                ) {
                    cell = 5
                } else if (
                    player1List.containsAll(listOf(1, 3, 4))
                ) {
                    cell = 2
                } else if (
                    player1List.containsAll(listOf(1, 5, 7))
                ) {
                    cell = 3
                } else if (
                    player1List.containsAll(listOf(1, 3, 5)) ||
                    player1List.containsAll(listOf(1, 2, 4))
                ) {
                    cell = 7
                } else if (player1List.containsAll(listOf(3, 5, 9))) {
                    cell = 1
                }

dave08

01/29/2018, 3:20 AM

It might also be easier on people to spot better shorcuts for you...

Joe

02/02/2018, 12:53 PM

That’s right. I keep forgetting that

let

actually returns something.

uhe

02/02/2018, 3:03 PM

imo the

if else

is more readable

➕ 14

marcinmoskala

02/10/2018, 5:38 AM

I would like to know your opinion. I had following function:

subscriptions += repository.getQuests()
        .applySchedulers()
        .smartSubscribe(
                onSuccess = view::showList and this::updateUpTrackingList,
                onError = view::handleError,
                onFinish = view::hideLoader
        )

Which is, as you can guess, RxJava usage. On success I use both show list on view instance (this is in presenter) and I update tracking list:

private fun updateUpTrackingList(quests: List<Quest>) {
    AppDatabase.addAppsToInstall(*quests.map { it.pkg }.toTypedArray())
}

and

is obviously commonly used function in my projects:

infix fun <T> ((T) -> Unit).and(f: (T) -> Unit): (T) -> Unit = { this(it); f(it) }

I had to add buffering, but I wanted to keep nice descriptive form of functions passing. So I made following function:

private var previousList: List<Quest>? = null

private fun ifChanged(onListChanged: (List<Quest>) -> Unit) = fun(list: List<Quest>) {
    if(previousList != list) {
        previousList = list
        onListChanged(list)
    }
}

And I use it this way:

subscriptions += repository.getQuests()
        .applySchedulers()
        .smartSubscribe(
                onSuccess = ifChanged(view::showList and this::updateUpTrackingList),
                onError = view::handleError,
                onFinish = view::hideLoader
        )

For me it looks great but I am not sure if it is not too complex for other people. What do you think? @mg6maciej? Functional programming passionates? Everyone? PS. If I would have function delegate then I could even extract this buffering as a common patter (my proposition for this functionality is waiting on KEEP)

elect

02/14/2018, 10:24 AM

any better alternative to this?

var navEarliestChild = g.navWindow!!
            while (navEarliestChild.parentWindow != null && navEarliestChild.parentWindow!!.flags has Wf.ChildMenu)
                navEarliestChild = navEarliestChild.parentWindow!!

Title

elect

02/14/2018, 10:24 AM

any better alternative to this?

var navEarliestChild = g.navWindow!!
            while (navEarliestChild.parentWindow != null && navEarliestChild.parentWindow!!.flags has Wf.ChildMenu)
                navEarliestChild = navEarliestChild.parentWindow!!

Andreas Sinz

02/14/2018, 10:44 AM

@elect use recursion

elect

02/14/2018, 11:31 AM

uhm, smells overkill

but I'll give it a try

Andreas Sinz

02/14/2018, 11:37 AM

https://kotlinlang.org/docs/reference/functions.html#tail-recursive-functions

elect

02/14/2018, 3:39 PM

cool, I didnt know it, thanks!

Max Russek

02/14/2018, 10:06 PM

Also I have hunch that

generateSequence

might help https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.sequences/generate-sequence.html

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