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
d

dave08

05/01/2018, 4:43 AM
fun ReceiveChannel. toDeferred() = async { single() }
, @spierce7 maybe, but probably not such good practice in coroutines to do such a thing though...
s

spierce7

05/01/2018, 1:36 PM
why not a good practice to do such a thing?
d

dave08

05/01/2018, 1:41 PM
Coroutines is a whole different way of looking at concurrency, it doesn't need composition as much as Rx, but rather supports linear code just as if there wasn't any concurrency and everything was running on one thread. You shouldn't really need to use Deferred or any coroutine launcher so often, only at the outer level of code, the rest should all be suspend fun... @Jonathan explained this very well in one of the Github coroutine issues, I can't find it right now though 🙁
s

spierce7

05/01/2018, 1:46 PM
How would you recommend I do this without using Channel? I need a bridge (similar to rx Subject) between the coroutine world and the non coroutine world:
class AuthWorkflow : AbstractWorkflow<Unit, Unit>() {
  protected val resultChannel = Channel<Unit>()
  
  override fun start(input: Unit): Deferred<Unit> {
    return resultChannel.toDeferred()
  }
  
  override fun abort() {
  }
  
  fun finish() {
    resultChannel.offer(Unit)
  }
}
d

dave08

05/01/2018, 1:57 PM
You need this to be called in Java? Otherwise, you could make
start
into a
suspend fun
and call
single()
or
receive()
. The Channel is fine, the deferred might not be necessary...
But for one result, why do you need a Channel?
You could have a suspend fun return the result straight away..
s

spierce7

05/01/2018, 2:15 PM
because the result won't return until a later time.
the example I showed is incomplete. Basically something will call
start
and receive a deferred back. The deferred won't have a result until the AuthWorkflow is complete, at which point it will return, return and the person who called start() will then be notified
Is there a better way to do this with coroutines. I admit I am stuck in an rx world in my mind
d

dave08

05/01/2018, 3:18 PM
It doesn't matter that the result is not till later, it'll suspend just as long as whatever you're calling that needs to be waited for is adapted to suspend too... @spierce7
s

spierce7

05/01/2018, 3:20 PM
Can you show me in code? How would I have that function suspend, and then stop from suspending when the result is there?
d

dave08

05/01/2018, 3:21 PM
What do you need to wait for in there @spierce7 ?
If it's Retrofit, there's a few libs to
await()
the result.. then you call that in your suspend function and until the result is not there, it won't return
Coroutines are like a callback, suspending happens until the "callback" receives the result, but instead of having to wrap all the code in a lambda, it just returns the result to the next instruction in the coroutine flow.
s

spierce7

05/01/2018, 6:01 PM
So it's probably in most cases awaiting user input. In the case of the AuthWorkflow, the
start
function is called when the user first goes to the auth / login page, and the
Deferred
that will return from it will complete when the user successfully logs in
make sense?
d

dave08

05/01/2018, 6:11 PM
You're on Android using a WebView? Or using an httpclient to log in? If so, one of them should have a callback you can wrap into a
suspend fun login()
function...
On Android if I want to request a Permission, I have the following: https://gist.github.com/dave08/f8d6a717f25b426e00fcfabc73b7197d.
That way my code is linear...
s

spierce7

05/01/2018, 6:17 PM
no, I'm not using a webview.
d

dave08

05/01/2018, 6:18 PM
so you don't need a whole class for login... nor a callback.. you just call
login()
as if it would return right away and let it suspend until the result comes in, the next steps will be stored in a continuation until the result arrives, and then the code continues
What are you using? Retrofit?
Another client?
s

spierce7

05/01/2018, 6:18 PM
no
this isn't an http call
d

dave08

05/01/2018, 6:19 PM
So what is it? Any lib. you can point to?
s

spierce7

05/01/2018, 6:19 PM
no, home grown lib
basically, start is called, and it will show the auth screen
d

dave08

05/01/2018, 6:20 PM
How do you get a result? With a callback?
s

spierce7

05/01/2018, 6:20 PM
and
start
returns a
Deferred
, and that
Deferred
, won't complete until after the user has successfully logged in
make sense?
d

dave08

05/01/2018, 6:21 PM
How do you get the Deferred? Where is it coming from? You need to go to the root to see if it can be turned into a suspend fun...
A callback can be adapted like in my gist
s

spierce7

05/01/2018, 6:22 PM
That's what I'm trying to figure out. Where does the deferred come from? The only way I've found to do it is to take a channel, and then have it return a deferred
is there a way for me to instead of taking a channel and convert it to a deferred, to just use a deferred from the start?
d

dave08

05/01/2018, 6:23 PM
Yes,
CompletableDeferred
. But you need to call it from some callback or something...
Same as my gist, but instead I make a
suspend fun
s

spierce7

05/01/2018, 6:26 PM
CompletableDeferred
is exactly what I need
thanks 🙂
d

dave08

05/01/2018, 6:26 PM
Deferred can also used when you need to run blocking api in
async(MyThreadPool) { ... }
and you get a Deferred as a result
But only when you don't have any callbacks to use...
s

spierce7

05/01/2018, 6:26 PM
thanks 🙂
d

dave08

05/01/2018, 6:27 PM
Good luck 😉