My business layer doesn't include Compose, but I'd like a method in it to suspend while waiting for ...

# compose

[David W]

My business layer doesn't include Compose, but I'd like a method in it to suspend while waiting for the user to respond to a dialog.
Showing the dialog uses @Composable, which doesn't exist in the business layer. Any patterns on how to structure that? I'll put what I have so far in the thread.

[David W]

Business module

suspend fun installFromUnknownSource(
        promptUserToReplaceExistingFolder: suspend (modInfo: ModInfo) -> Boolean
    )

[David W]

Dialog

@Composable
suspend fun DuplicateModAlertDialog(modInfo: ModInfo): Boolean {
    return suspendCoroutine { cont ->
      // stuff
      cont.resume(...)
   }
}

[David W]

Usage (the part that doesn't compile due to lacking Composable)

installFromUnknownSource(
    promptUserToReplaceExistingFolder = { modInfo ->
        DuplicateModAlertDialog(modInfo)
    })

[David W]

can't tell if i'm being dumb or trying to do something that shouldn't be done (not mutually exclusive)

[Adam Powell]

You might be interested in how SnackbarHostState publishes data for composables to display. It uses a suspend function to show a notification and get a return value for whether the snackbar was dismissed or if the user pressed a button for that message https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:compose/material/material/src/commonMain/kotlin/androidx/compose/material/SnackbarHost.kt;l=60?q=SnackbarHostState&sq=

[David W]

Very interesting, thank you! Took me a bit to get a chance to look.

So it essentially decouples the Snackbar from the listener. Calling showSnackbar creates a new (observable) state that contains a continuation, then suspends. The Snackbar is then created/shown in response to the newly created state and invokes the continuation when the user interacts with it.

[David W]

Having that "singleton" state variable is the decoupling that's needed to allow the communication between the layer without Composable and the layer with

[Adam Powell]

right. And since it's state, it can be presented in 0-N places simultaneously if the situation calls for it

[Adam Powell]

nothing is "consumed" unless it's acted on, and it doesn't particularly matter which presentation is acted on

[Adam Powell]

and if the caller of showSnackbar no longer cares, it can cancel its call and it will be removed from the queue; if it was currently being shown it will move on to the next one

[David W]

canceling the suspending call with invoke

finally {
            currentSnackbarData = null
        }

?

[David W]

and from there the next suspending call, which was waiting for the Mutex, will start, creating a new toast

[Adam Powell]

Yep