what's the correct way to show a toast triggered by the viewModel in compose?

# compose

[Lucca Beurmann]

what's the correct way to show a toast triggered by the viewModel in compose?

[Dmitrii Smirnov]

you shall think in declarative way:
UI is a function of state, which means that you have no method "showToast" triggered by VM, but there is parameter e.g. "toastShown" in your state, which VM changes

[Lucca Beurmann]

Humm, so the solution would be create a LaunchedEffect with isTostVisible state as a key and show the toast whenever the state is updated to true?

[Colton Idle]

@Lucca Beurmann try to keep your message as one single post on slack in order to help with threading conversations.

https://kotlinlang.slack.com/archives/CJLTWPH7S/p1612194022136600

[dewildte]

I expose a Flow<SideEffect> and have who ever controls the showing of the Toast or SnackBar collect it.

[dewildte]

SideEffect being a sealed class.

[Lucca Beurmann]

DisposableEffect(key1 = lifecycleOwner) {
        viewModel.showErrorToast.observeEvent(lifecycleOwner) {
        Toast.makeText(
            context,
            context.getString(R.string.author_details_images_erro
            Toast.LENGTH_SHORT
        )
            .show()
    }
    onDispose {
        viewModel.showErrorToast.removeObservers(lifecycleOwner)
    }
}

Currently that's how i'm observing the viewModel event

[dewildte]

Example_kt.kt

[Lucca Beurmann]

there's a similar example in the SideEffects docs: https://developer.android.com/jetpack/compose/side-effects

[Lucca Beurmann]

but how you are setting up the this flow collection in your composables?

[dewildte]

Collecting it from a LaunchedEffect works fine.

[dewildte]

Just ensure that effect is not being called more then once.

[Lucca Beurmann]

thanks for the answer

[Lucca Beurmann]

yeah i ensured that my disposable effect is being called just once, my main doubt was how to collect/observe the event from the viewModel

[Tash]

If you find yourself needing to show a snackbar instead, check out https://developer.android.com/reference/kotlin/androidx/compose/material/SnackbarHostState