What is the difference between `LaunchedEffect` and `remember`? `LaunchedEffect` uses `remember` i...

# compose

[Abhimanyu]

What is the difference between LaunchedEffect and remember?

LaunchedEffect uses remember internally.

@Composable
@NonRestartableComposable
@OptIn(InternalComposeApi::class)
fun LaunchedEffect(
    key1: Any?,
    block: suspend CoroutineScope.() -> Unit
) {
    val applyContext = currentComposer.applyCoroutineContext
    remember(key1) { LaunchedEffectImpl(applyContext, block) }
}

[Abhimanyu]

The additions I see in LaunchedEffect ,
1. coroutine scope
2. Returns the calculated data.

[Abhimanyu]

If I don’t need coroutine scope and the returned data will not be used as the block updates another mutable state in the Composable,

should I use remember or LaunchedEffect ?

[Abhimanyu]

Example

@Composable
fun Test(
  para1: Int,
) {
  var result = remember {
    mutableStateOf("")
  }

  remember(para1) {
    aMethodsWithCallbacks() { updatedResult: String -> 
        result = updatedResult
    }
  }

  return result
}

vs

@Composable
fun Test(
  para1: Int,
) {
  var result = remember {
    mutableStateOf("")
  }

  LaunchedEffect(para1) {
    aMethodsWithCallbacks() { updatedResult: String -> 
        result = updatedResult
    }
  }

  return result
}

[Chris Sinco [G]]

remember is generally used for any state you need persisted between recompositions. LaunchedEffect is a specific side effect: https://developer.android.com/jetpack/compose/side-effects

[Abhimanyu]

To add,
Both works as intended (it seems like that so far)

So, checking on the preferred approach.

[Chris Sinco [G]]

It’s not really one over the other. LaunchedEffect has a specific use case, as detailed in the documentation

[mattinger]

If you have a piece of state that needs to be remembered across re-composition, you would use remember (usually with "mutableStateOf").

LaunchedEffect is for running a coroutine that has side effects. How often and when the coroutine launches depends on the "key" parameters as detailed in the documents mentioned above.