Hi I m practicing Compose for desktop and I m stuck with the kotlinlang #compose-desktop

Hi! I’m practicing Compose for desktop and I’m stuck with the problem: I have “screenState: StateFlow” value with state for my UI (sealed class) From UI I use default approach “screenState.collectAsFlow()” to trigger recomposition if state changes and I have method “subscribe(chatRoom: ChatRoom)” in my ApplicationController (aka view model for desktop) which calls to a useCase and returns Flow<Message>. Emitter takes my state and makes a copy with a new message but from time to time Compose ignores (or misses) new state value. Screenshots in thread.

Compose state

State flow in app controller

chat message emitter

Zach Klippenstein (he/him) [MOD]

04/30/2021, 4:46 PM

You need to copy the list as well, or use

SnapshotStateList

✅ 1

Some other notes: 1. It’s considered a bad practice to implement

CoroutineScope

directly from classes that do other things. Store the scope in a property instead (elizarov has written about this). 2. No need to pass

Dispatchers.Main

collectAsState

, it will use the compose dispatcher by default (which is basically

Dispatchers.Main

with extra features). 3. There’s a potential data race in your

subscribe

coroutine, if there are multiple instances of that coroutine running concurrently. One way to fix would be wrap the body of the

collect

with a

Mutex

Semyon Zadorozhnyi

04/30/2021, 4:52 PM

Noted) Problem solved, thanks a lot!

No need to pass
Dispatchers.Main
to
collectAsState

That’s just attempt to fix the problem by changing something random 😄

4 Views

#compose-desktop Join Slack