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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