kotlin-coroutines-expertlisted

# Kotlin Coroutines Expert ## Overview Authoritative guide for asynchronous programming, reactive data streams, and cancellation/exception safety in this Android app. --- ## 1. Structured Concurrency - Always launch coroutines within a defined `CoroutineScope` (e.g., `viewModelScope` with `applicationExceptionHandler`). - Use `coroutineScope` or `supervisorScope` to group concurrent tasks. - **Never use `GlobalScope`** (causes memory leaks and uncontrollable lifetimes). ```kotlin suspend fun loadDashboardData(): DashboardData = supervisorScope { val userDeferred = async { userRepo.getUser() } val stepsDeferred = async { stepsRepo.getTodaySteps() } DashboardData( user = userDeferred.await(), steps = stepsDeferred.await() ) } ``` --- ## 2. Exception & Cancellation Safety - Top-level scopes should use `CoroutineExceptionHandler`. - Never swallow `CancellationException` — if caught, rethrow it to allow proper cancellation propagation. - For network calls, catch specific domain exceptions (`IOException`, `HttpException`) instead of a generic empty `catch (e: Exception)`. --- ## 3. Reactive Streams (Flow & StateFlow) - Expose read-only `StateFlow<T>` or `SharedFlow<T>` from ViewModels; keep `MutableStateFlow` private. - For One-Shot UI events (navigation, toast, dialog), use `Channel<Event>` with `receiveAsFlow()` or `SharedFlow<Event>(replay = 0)`. **Never use sticky MutableLiveData**. - Use `flowOn(Dispatchers.IO)` for heavy data trans