kotlin-coroutines-expert

name	kotlin-coroutines-expert
description	Expert patterns for Kotlin Coroutines and Flow, covering structured concurrency, error handling, and testing.
type	skill
created	2026-02-27T00:00:00.000Z
domain	software-development
category	mobile
risk	safe
source	community
tags	["skill","software-development","mobile","kotlin","coroutines"]

Kotlin Coroutines Expert

Overview

A guide to mastering asynchronous programming with Kotlin Coroutines. Covers advanced topics like structured concurrency, Flow transformations, exception handling, and testing strategies.

When to Use This Skill

• Use when implementing asynchronous operations in Kotlin.
• Use when designing reactive data streams with Flow.
• Use when debugging coroutine cancellations or exceptions.
• Use when writing unit tests for suspending functions or Flows.

Step-by-Step Guide

1. Structured Concurrency

Always launch coroutines within a defined CoroutineScope. Use coroutineScope or supervisorScope to group concurrent tasks.

suspend fun loadDashboardData(): DashboardData = coroutineScope {
    val userDeferred = async { userRepo.getUser() }
    val settingsDeferred = async { settingsRepo.getSettings() }
    
    DashboardData(
        user = userDeferred.await(),
        settings = settingsDeferred.await()
    )
}

2. Exception Handling

Use CoroutineExceptionHandler for top-level scopes, but rely on try-catch within suspending functions for granular control.

val handler = CoroutineExceptionHandler { _, exception ->
    println("Caught $exception")
}

viewModelScope.launch(handler) {
    try {
        riskyOperation()
    } catch (e: IOException) {
        // Handle network error specifically
    }
}

3. Reactive Streams with Flow

Use StateFlow for state that needs to be retained, and SharedFlow for events.

// Cold Flow (Lazy)
val searchResults: Flow<List<Item>> = searchQuery
    .debounce(300)
    .flatMapLatest { query -> searchRepo.search(query) }
    .flowOn(Dispatchers.IO)

// Hot Flow (State)
 uiState: StateFlow<UiState> = _uiState.asStateFlow()