🧵 Compose Effects enable you to launch efficient side-effects without unnecessary operations.

Jetpack Compose provides three primary side-effect handlers: LaunchedEffect, DisposableEffect, and SideEffect. Among them, LaunchedEffect is particularly useful for executing side effects whenever a specified key changes. However, it is best suited for coroutine-based tasks, as it creates a new coroutine scope and re-launches the task whenever the key changes, canceling any previously running job.

This behavior can introduce unnecessary overhead by creating redundant coroutine scopes and tasks, even in cases where you simply want to track key changes and launch a non-coroutine based task without re-triggering the effect during recomposition.

Compose Effects offer a straightforward solution to avoid this minor overhead by providing APIs, such as:

var count by remember { mutableIntStateOf(0) }

 // LaunchedEffect will launch a new coroutine scope regardless the task is related to the coroutines.
 // You can avoid this by using RememberedEffect for executing non-coroutine tasks.
- LaunchedEffect(key1 = count) {
+ RememberedEffect(key1 = count) {
    Log.d(tag, "$count")
}

Button(onClick = { count++ }) {
    Text("Count: $count")
}

If you're using Version Catalog, you can configure the dependency by adding it to your libs.versions.toml file as follows:

[versions]
#...
composeEffects = "0.1.1"

[libraries]
#...
compose-effects = { module = "com.github.skydoves:compose-effects", version.ref = "composeEffects" }

Add the dependency below to your module's build.gradle.kts file:

dependencies {
    implementation("com.github.skydoves:compose-effects:$version")
    
    // if you're using Version Catalog
    implementation(libs.compose.effects)
}

For Kotlin Multiplatform, add the dependency below to your module's build.gradle.kts file:

sourceSets {
    val commonMain by getting {
        dependencies {
            implementation("com.github.skydoves:compose-effects:$version")
        }
    }
}

RememberedEffect is a side-effect API that executes the provided lambda function when it enters the composition and re-executes it whenever key changes.

Unlike LaunchedEffect, RememberedEffect does not create or launch a new coroutine scope on each key change, making it a more efficient option for remembering the execution of side-effects, if you don't to launch a coroutine task.

var count by remember { mutableIntStateOf(0) }

// Unlike LaunchedEffect, this won't launch a new coroutine scope when the key changes.
RememberedEffect(key1 = count) {
    Log.d(tag, "$count")
}

Button(onClick = { count++ }) {
    Text("Count: $count")
}

Compose Effects ViewModel provides side-effects/CompositionLocal APIs related to ViewModel.

Add the dependency below to your module's build.gradle.kts file:

dependencies {
    implementation("com.github.skydoves:compose-effects-viewmodel:$version")
}

In certain scenarios, managing ViewModel lifecycles at a more Composable function-scoped level is preferable to broader scopes like Activity or Jetpack Navigation. For example, you may need to assign dedicated ViewModel instances for bottom sheets, dialogs inside a LazyColumn, or other complex UI components to prevent unintended reuse of the same ViewModel across different scopes. This ensures better isolation and state management, particularly in cases where UI elements require independent lifecycle handling.

Consider the following scenario: you have a list of items, and clicking on an item opens a dialog specific to that item. Initially, everything appears to work fine. However, if you click on another item, you'll notice that the same ViewModel instance is being reused, regardless of how many times the dialog is dismissed. This can lead to unintended state persistence across different dialogs, affecting the expected behavior.

val items = List(50) { "item$it" }
var visibleDialog by remember { mutableStateOf(false) }

LazyColumn(modifier = Modifier.fillMaxSize()) {
  items(items = items, key = { it }) { item ->
    Box(
      modifier = Modifier
        .fillMaxSize()
        .height(500.dp)
        .clickable { visibleDialog = !visibleDialog }
    ) {
      Text(text = item)

      Box(
        modifier = Modifier
          .height(1.dp)
          .background(Color.Gray)
          .align(Alignment.BottomCenter)
      )
    }

    if (visibleDialog) {
      val vm: DialogViewModel = hiltViewModel() // reused
      val text by vm.state.collectAsState()

      Dialog(onDismissRequest = { visibleDialog = false }) {
        Box(
          modifier = Modifier
            .fillMaxWidth()
            .height(450.dp)
            .background(Color.Blue)
            .clickable { vm.onClicked(item) }
        ) {
          Text(text = text, color = Color.White)
        }
      }
    }
  }
}

You can ensure that each dialog gets a new ViewModel instance by using ViewModelStoreScope, as demonstrated in the following code snippet:

ViewModelStoreScope(key = item) {
  if (visibleDialog) {
    val vm: DialogViewModel = hiltViewModel() // this will be scoped to the ViewModelStoreScope
    val text by vm.state.collectAsState()

    Dialog(onDismissRequest = { visibleDialog = false }) {
      Box(
        modifier = Modifier
          .fillMaxWidth()
          .height(450.dp)
          .background(Color.Blue)
          .clickable { vm.onClicked() }
      ) {
        Text(text = text, color = Color.White)
      }
    }
  }
}

ViewModelStoreScope is a disposable side-effect that creates a new ViewModelStore and ViewModelStoreOwner, scoping view models to a local store and ensuring the store is cleared when the it leaves the composition. When you need to scope ViewModels to a specific Composable-based lifecycle, ViewModelStoreScope provides an effective solution.

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Designed and developed by 2025 skydoves (Jaewoong Eum)

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

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