Jetpack Compose Side Effects — Complete Guide

In this tutorial, you'll learn about Jetpack Compose Side Effects. We cover key concepts, practical examples, and best practices to help you understand and apply this topic effectively.

The Problem

Your network call runs on every recomposition, the timer restarts constantly, or the Firebase Observer accumulates multiple subscriptions.

Wrong Approach ❌

@Composable
fun BadLoader() {
    // Runs on EVERY recomposition — infinite loop!
    val result = viewModel.loadData()

    // Side effect without key — restarts on every recomposition
    LaunchedEffect(Unit) {
        viewModel.loadData() // Okay, but...
    }
}

@Composable
fun LeakyObserver() {
    // Added every recomposition — never disposed
    DisposableEffect(Unit) {
        firestore.addSnapshotListener { /* callback */ }
        onDispose { } // Empty! Never removes listener
    }
}

Output: Network call floods the server. Memory leak from unremoved listeners.

Right Approach ✅

@Composable
fun GoodSideEffects(userId: String) {
    // Key changes when userId changes — restarts the coroutine
    LaunchedEffect(userId) {
        viewModel.loadData(userId)
    }

    // Properly cleaned up
    DisposableEffect(userId) {
        val listener = firestore.document("users/$userId")
            .addSnapshotListener { snapshot, _ -> /* handle */ }

        onDispose {
            listener.remove() // Cleanup!
        }
    }

    // SideEffect for non-Compose callbacks
    SideEffect {
        analytics.setUserId(userId)
    }
}

Output: Network call runs once per key. Listener cleaned up on disposal.

Prevention

• Always provide stable keys to LaunchedEffect and DisposableEffect.
• Use LaunchedEffect for async work, DisposableEffect for cleanup.
• Use SideEffect for non-Compose code that must run on every recomposition.
• Never put suspend functions directly in a composable body.

Common Mistakes with compose effect

1. Using foldl instead of foldl' causing stack overflow on large lists
2. Forgetting deriving (Show, Eq) on custom data types needed for debugging
3. Placing the wildcard pattern first in case expressions, making all subsequent patterns unreachable

These mistakes appear frequently in real-world Android code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

FAQ