rxjava-to-coroutines-migration

RxJava to Kotlin Coroutines Migration Skill

A specialized skill designed to safely and idiomatically refactor Android or Kotlin codebases from RxJava to Kotlin Coroutines and Flow.

Migration Mapping Guide

When migrating RxJava components to Kotlin Coroutines, use the following standard mappings:

1. Base Types

• Single<T> -> suspend fun ...(): T
  • A single asynchronous value.
• Maybe<T> -> suspend fun ...(): T?
  • A single asynchronous value that might not exist.
• Completable -> suspend fun ...()
  • An asynchronous operation that completes without a value.
• Observable<T> -> Flow<T>
  • A cold stream of values.
• Flowable<T> -> Flow<T>
  • Coroutines Flow natively handles backpressure.

2. Subjects to Hot Flows

• PublishSubject<T> -> MutableSharedFlow<T>
  • Broadcasts events to multiple subscribers. Use MutableSharedFlow(extraBufferCapacity = ...) if buffering is needed.
• BehaviorSubject<T> -> MutableStateFlow<T>
  • Holds state and emits the current/latest value to new subscribers. Requires an initial value.
• ReplaySubject<T> -> MutableSharedFlow<T>(replay = N)
  • Replays the last N emitted values to new subscribers.

3. Schedulers to Dispatchers

• Schedulers.io() -> Dispatchers.IO
• Schedulers.computation() -> Dispatchers.Default
• AndroidSchedulers.mainThread() -> Dispatchers.Main
• Context Switching: subscribeOn and observeOn are typically replaced by withContext(Dispatcher) or flowOn(Dispatcher) for Flows.

4. Operators

• map -> map
• filter -> filter
• flatMap -> flatMapMerge (concurrent) or flatMapConcat (sequential)
• switchMap -> flatMapLatest
• doOnNext / doOnSuccess -> onEach
• onErrorReturn / onErrorResumeNext -> catch { emit(...) }
• startWith -> onStart { emit(...) }
• combineLatest -> combine
• zip -> zip
• delay -> delay (suspend function) or onEach { delay(...) }