I used to rely heavily on LaunchedEffect for handling asynchronous operations in Compose,but lately, I’ve realized that produceState might allow for a cleaner and more concise implementation.
So, I asked several AI assistants for their opinions and compared their responses.
🤔 GitHub Copilot
- LaunchedEffect: Suitable for asynchronous operations that modify externally managed states (e.g., ViewModel).
- produceState: Best for generating and managing asynchronous data directly within Compose.
- Choose LaunchedEffect for externally managed state, and produceState for internally managed state.
@Composable
fun ExampleScreen(viewModel: MyViewModel = viewModel()) {
// LaunchedEffect: Update externally managed state asynchronously
val externalState by viewModel.uiState.collectAsState()
LaunchedEffect(Unit) {
viewModel.loadData() // Update external state asynchronously
}
// produceState: Generate and manage asynchronous data inside Compose
val internalState by produceState(initialValue = "Loading...", key1 = viewModel) {
value = viewModel.loadDataSync() // Assign result to internal state
}
Column {
Text("LaunchedEffect State: $externalState")
Text("ProduceState State: $internalState")
}
}
🤔 ChatGPT
- Use LaunchedEffect when updating existing state through side effects.
- Use produceState when treating the result of an async operation as a state itself.
- “Generate” with produceState, “manipulate” with LaunchedEffect.
@Composable
fun UserScreen(userId: String) {
var user by remember { mutableStateOf<User?>(null) }
LaunchedEffect(userId) { user = api.fetchUser(userId) } // Update existing state
val userState by produceState<User?>(initialValue = null, key1 = userId) {
value = api.fetchUser(userId) // Convert async result directly to state
}
Text("Launched: ${user?.name ?: "Loading..."}")
Text("Produced: ${userState?.name ?: "Loading..."}")
}
🤔 Gemini
- produceState: Ideal for exposing results of suspend functions or external data sources as reactive State for the UI.
- LaunchedEffect: Tied to the composable’s lifecycle, suited for one-time async actions or UI event triggers (e.g., showing a snackbar).
- State management: produceState handles state automatically, while LaunchedEffect requires manual updates via mutableStateOf.
@Composable
fun UserDataState(userId: String): State<User?> = produceState<User?>(
initialValue = null,
key1 = userId // Automatically restarts when key changes
) {
value = fetchUserFromApi(userId)
}
@Composable
fun EventSnackbar(viewModel: MyViewModel) {
val scope = rememberCoroutineScope() // Scope for showing snackbar
LaunchedEffect(Unit) { // Runs once on first composition
viewModel.uiEvents.collect { event ->
// Receive UI event and trigger a side effect (e.g., show snackbar)
scope.launch { SnackbarHostState.showSnackbar("Received event!") }
}
}
}
🤔 Summary
- LaunchedEffect: Used when updating externally managed states (e.g., ViewModel) through asynchronous operations.
- produceState: Used when generating and managing the result of asynchronous processing directly as state within Compose.
- If the state is managed externally, use LaunchedEffect; if it’s internally generated, use produceState.
- LaunchedEffect requires manual state updates, while produceState automatically manages state.
- Use LaunchedEffect to update external state, and produceState to generate internal state.
- LaunchedEffect manipulates existing state through side effects.
- produceState creates new state from asynchronous results.
- Operate state = LaunchedEffect / Generate state = produceState
- produceState: Ideal for exposing asynchronous results as automatically managed State objects for the UI.
- LaunchedEffect: Used to manually update existing states (e.g., ViewModel’s state) or trigger side effects such as showing a snackbar.
- Where the state is managed: If it’s generated within Compose → use produceState.
- Where the state is managed: If it’s controlled outside Compose (e.g., ViewModel) → use LaunchedEffect.
👉 【AIコーディング】非同期処理の極意！LaunchEffect と produceState の使い分けで Jetpack Compose を制す
