https://kotlinlang.org logo
Channels
100daysofcode
100daysofkotlin
100daysofkotlin-2021
advent-of-code
aem
ai
alexa
algeria
algolialibraries
amsterdam
android
android-architecture
android-databinding
android-studio
androidgithubprojects
androidthings
androidx
androidx-xprocessing
anime
anko
announcements
apollo-kotlin
appintro
arabic
argentina
arkenv
arksemdevteam
armenia
arrow
arrow-contributors
arrow-meta
ass
atlanta
atm17
atrium
austin
australia
austria
awesome-kotlin
ballast
bangladesh
barcelona
bayarea
bazel
beepiz-libraries
belgium
benchmarks
berlin
big-data
books
boston
brazil
brikk
budapest
build
build-tools
bulgaria
bydgoszcz
cambodia
canada
carrat
carrat-dev
carrat-feed
chicago
chile
china
chucker
cincinnati-user-group
cli
clikt
cloudfoundry
cn
cobalt
code-coverage
codeforces
codemash-precompiler
codereview
codingame
codingconventions
coimbatore
collaborations
colombia
colorado
communities
competitive-programming
competitivecoding
compiler
compose
compose-android
compose-desktop
compose-hiring
compose-ios
compose-mp
compose-ui-showcase
compose-wear
compose-web
confetti
connect-audit-events
corda
cork
coroutines
couchbase
coursera
croatia
cryptography
cscenter-course-2016
cucumber-bdd
cyprus
czech
dagger
data2viz
databinding
datascience
dckotlin
debugging
decompose
decouple
denmark
deprecated
detekt
detekt-hint
dev-core
dfw
docs-revamped
dokka
domain-driven-design
doodle
dsl
dublin
dutch
eap
eclipse
ecuador
edinburgh
education
effective-kotlin
effectivekotlin
emacs
embedded-kotlin
estatik
event21-community-content
events
exposed
failgood
fb-internal-demo
feed
firebase
flow
fluid-libraries
forkhandles
forum
fosdem
fp-in-kotlin
framework-elide
freenode
french
fritz2
fuchsia
functional
funktionale
gamedev
ge-kotlin
general-advice
georgia
geospatial
german-lang
getting-started
github-workflows-kt
glance
godot-kotlin
google-io
gradle
graphic
graphkool
graphql
graphql-kotlin
graviton-browser
greece
grpc
gsoc
gui
hackathons
hacktoberfest
hamburg
hamkrest
helios
helsinki
hexagon
hibernate
hikari-cp
hire-me
hiring
hiring-french
hongkong
hoplite
http4k
hungary
hyderabad
image-processing
india
indonesia
inkremental
intellij
intellij-plugins
intellij-tricks
internships
introduce-yourself
io
ios
iran
israel
istanbulcoders
italian
jackson-kotlin
jadx
japanese
jasync-sql
java-to-kotlin-refactoring
javadevelopers
javafx
javalin
javascript
jdbi
jhipster-kotlin
jobsworldwide
jpa
jshdq
juul-libraries
jvm-ir-backend-feedback
jxadapter
k2-early-adopters
kaal
kafka
kakao
kalasim
kapt
karachi
karg
karlsruhe
kash_shell
kaskade
kbuild
kdbc
kgen-doc-tools
kgraphql
kinta
klaxon
klock
kloudformation
kmdc
kmm-español
kmongo
knbt
knote
koalaql
koans
kobalt
kobweb
kodein
kodex
kohesive
koin
koin-dev
komapper
kondor-json
kong
kontent
kontributors
korau
korean
korge
korim
korio
korlibs
korte
kotest
kotest-contributors
kotless
kotlick
kotlin-asia
kotlin-beam
kotlin-by-example
kotlin-csv
kotlin-data-storage
kotlin-foundation
kotlin-fuel
kotlin-in-action
kotlin-inject
kotlin-latam
kotlin-logging
kotlin-multiplatform-contest
kotlin-mumbai
kotlin-native
kotlin-pakistan
kotlin-plugin
kotlin-pune
kotlin-roadmap
kotlin-samples
kotlin-sap
kotlin-serbia
kotlin-spark
kotlin-szeged
kotlin-website
kotlinacademy
kotlinbot
kotlinconf
kotlindl
kotlinforbeginners
kotlingforbeginners
kotlinlondon
kotlinmad
kotlinprogrammers
kotlinsu
kotlintest
kotlintest-devs
kotlintlv
kotlinultimatechallenge
kotlinx-datetime
kotlinx-files
kotlinx-html
kotrix
kotson
kovenant
kprompt
kraph
krawler
kroto-plus
ksp
ktcc
ktfmt
ktlint
ktor
ktp
kubed
kug-leads
kug-torino
kvision
kweb
lambdaworld_cadiz
lanark
language-evolution
language-proposals
latvia
leakcanary
leedskotlinusergroup
lets-have-fun
libgdx
libkgd
library-development
lincheck
linkeddata
lithuania
london
losangeles
lottie
love
lychee
macedonia
machinelearningbawas
madrid
malaysia
mathematics
meetkotlin
memes
meta
metro-detroit
mexico
miami
micronaut
minnesota
minutest
mirror
mockk
moko
moldova
monsterpuzzle
montreal
moonbean
morocco
motionlayout
mpapt
mu
multiplatform
mumbai
munich
mvikotlin
mvrx
myndocs-oauth2-server
naming
navigation-architecture-component
nepal
new-mexico
new-zealand
newname
nigeria
nodejs
norway
npm-publish
nyc
oceania
ohio-kotlin-users
oldenburg
oolong
opensource
orbit-mvi
osgi
otpisani
package-search
pakistan
panamá
pattern-matching
pbandk
pdx
peru
philippines
phoenix
pinoy
pocketgitclient
polish
popkorn
portugal
practical-functional-programming
proguard
prozis-android-backup
pyhsikal
python
python-contributors
quasar
random
re
react
reaktive
realm
realworldkotlin
reductor
reduks
redux
redux-kotlin
refactoring-to-kotlin
reflect
refreshversions
reports
result
rethink
revolver
rhein-main
rocksdb
romania
room
rpi-pico
rsocket
russian
russian_feed
russian-kotlinasfirst
rx
rxjava
san-diego
science
scotland
scrcast
scrimage
script
scripting
seattle
serialization
server
sg-user-group
singapore
skia-wasm-interop-temp
skrape-it
slovak
snake
sofl-user-group
southafrica
spacemacs
spain
spanish
speaking
spek
spin
splitties
spotify-mobius
spring
spring-security
squarelibraries
stackoverflow
stacks
stayhungrystayfoolish
stdlib
stlouis
strife-discord-lib
strikt
students
stuttgart
sudan
swagger-gradle-codegen
swarm
sweden
swing
swiss-user-group
switzerland
talking-kotlin
tallinn
tampa
teamcity
tegal
tempe
tensorflow
terminal
test
testing
testtestest
texas
tgbotapi
thailand
tornadofx
touchlab-tools
training
tricity-kotlin-user-group
trójmiasto
truth
tunisia
turkey
turkiye
twitter-feed
uae
udacityindia
uk
ukrainian
uniflow
unkonf
uruguay
utah
uuid
vancouver
vankotlin
vertx
videos
vienna
vietnam
vim
vkug
vuejs
web-mpp
webassembly
webrtc
wimix_sentry
wwdc
zircon
Powered by
Title
j

Jérémy CROS

10/12/2021, 3:31 PM
Hey guys 🙂 Was looking to do something like that but it doesn’t seem to be allowed
data class Foo(val a:Int, val b = 0)
val bar = Foo(a = 3, if(param) b = 5 /*else keep the default param */)
Is there an alternative other than
val bar = if(param) Foo(...) else Foo(...)
🇳🇴 3
h

Holden Easley

10/12/2021, 3:32 PM
Its not pretty but something like
Foo(a = 3).let { 
  if (param) it.copy(b = 5) else it
}
??
j

Jérémy CROS

10/12/2021, 3:39 PM
hmm, not sure I like it but it’s still an interesting alternative, thanks 🙂 will try with the actual code see how it feels
c

Connor Ford

10/12/2021, 3:41 PM
maybe this is more readable?
data class Foo(val a: Int, val b: Int = DEFAULT_B) {
    constructor(a: Int, p: Boolean): this(a, if (p) a else DEFAULT_B)

    companion object {
        private const val DEFAULT_B = 0
    }
}
c

CLOVIS

10/12/2021, 5:23 PM
Out of curiosity, what is the use-case? That seems like it would make the code much harder to understand
👍 1
s

Stephan Schroeder

10/13/2021, 7:24 AM
how about
data class Foo(val a:Int, val b = 0)
val bar = if(param) {
  Foo(3, 5)
} else {
  Foo(3)
}
e

ephemient

10/13/2021, 7:33 AM
with(Foo::class.primaryConstructor!!) {
    callBy(listOfNotNull("a" to 3, if (param) "b" to 5 else null).associate { (name, value) -> parameters.single { it.name == name } to value })
}
:blob-thinking-upside-down:
😆 4
🤣 1
IIRC Moshi does the equivalent of
Foo::class.java
    .getDeclaredConstructor(Int::class.java, Int::class.java, Int::class.java, kotlin.jvm.internal.DefaultConstructorMarker::class.java)
    .newInstance(3, if (param) 5 else 0 /* this value doesn't matter */, if (param) 0 else 2 /* bitmask */, null)
yeah you can see the implementation in https://github.com/square/moshi/pull/896
a

Alex

10/13/2021, 8:34 AM
@Jérémy CROS, what does param refer to?
j

Jérémy CROS

10/13/2021, 9:19 AM
It’s just a simple boolean with a business meaning. The solution first suggested is actually decently readable when used with the actual code.
return ActionInfrastructureUntilLevel(
    buildAction(instructionHumanized.humanInstruction.action),
    buildDirectionalInfrastructure(
        instructionHumanized.humanInstruction.infrastructure
    ),
    infrastructureUntilLevel.level,
    infrastructureUntilLevel.label
).let {
    if (isFirstInstructionAnInfrastructure)
        it.copy(template = R.string.sentence_template_infrastructure_until_level_first)
    else it
}
it’s basically a sentence builder with optional template parameter that are later used for translation. In that case, the simple if else as suggested by @Stephan Schroeder looks worse, IMO Won’t comment on @ephemient trolling me though 😛
👍 1
e

ephemient

10/13/2021, 9:27 AM
heh. sorry about trolling with callBy, I couldn't resist. although I think the synthetic constructor trick is actually useful until KT-18695 has a resolution, it's not worth it unless you're dealing with a situation where you may have a combinatorial explosion of default args
j

Jérémy CROS

10/13/2021, 9:29 AM
haha, yes. And thanks for the link btw, will monitor this one 🙂