This is a Cheatsheet for RxSwift developers interested in Apple's new Combine framework.
It's based on the following blog post: https://medium.com/gett-engineering/rxswift-to-apples-combine-cheat-sheet-e9ce32b14c5b
| RxSwift | Combine | |
|---|---|---|
| Deployment Target | iOS 8.0+ | iOS 13.0+ |
| Platforms supported | iOS, macOS, tvOS, watchOS, Linux | iOS, macOS, tvOS, watchOS, UIKit for Mac ¹ |
| Spec | Reactive Extensions (ReactiveX) | Reactive Streams (+ adjustments) |
| Framework Consumption | Third-party | First-party (built-in) |
| Maintained by | Open-Source / Community | Apple |
| UI Bindings | RxCocoa | SwiftUI ² |
| RxSwift | Combine | Notes |
|---|---|---|
| AnyObserver | AnySubscriber | |
| BehaviorRelay | ❌ | Simple wrapper around BehaviorSubject, could be easily recreated in Combine |
| BehaviorSubject | CurrentValueSubject | This seems to be the type that holds @State under the hood |
| Completable | ❌ | |
| CompositeDisposable | ❌ | |
| ConnectableObservableType | ConnectablePublisher | |
| Disposable | Cancellable | |
| DisposeBag | ❌ | |
| Driver | BindableObject (SwiftUI) | Both guarantee no failure, but Driver guarantees delivery on Main Thread. In Combine, SwiftUI recreates the entire view hierarachy on the Main Thread, instead. |
| Maybe | ❌ | |
| Observable | Publisher | |
| Observer | Subscriber | |
| PublishRelay | ❌ | Simple wrapper around PublishSubject, could be easily recreated in Combine |
| PublishSubject | PassthroughSubject | |
| ReplaySubject | ❌ | |
| ScheduledDisposable | ❌ | |
| SchedulerType | Scheduler | |
| SerialDisposable | ❌ | |
| Signal | ❌ | |
| Single | Future | Single behaves differently than Future. Seems the latter has no auto-disposal when finished |
| SubjectType | Subject | |
| TestScheduler | ❌ | There doesn't seem to be an existing testing scheduler for Combine code |
| RxSwift | Combine | Notes |
|---|---|---|
| amb() | ❌ | |
| asObservable() | eraseToAnyPublisher() | |
| asObserver() | eraseToAnySubject() | |
| bind(to:) | assign(to:on:) |
Assign uses a KeyPath which is really nice and useful. RxSwift needs a Binder / ObserverType to bind to. |
| buffer | buffer | |
| catchError | catch | |
| catchErrorJustReturn | replaceError(with:) | |
| combineLatest | combineLatest, tryCombineLatest | |
| compactMap | compactMap, tryCompactMap | |
| concat | append, prepend | |
| concatMap | ❌ | |
| create | AnyPublisher | AnyPublisher has an initializer with an anonymous closure, similar to Observable.create |
| debounce | debounce | |
| debug | ||
| deferred | Publishers.Deferred | |
| delay | delay | |
| delaySubscription | ❌ | |
| dematerialize | ❌ | |
| distinctUntilChanged | removeDuplicates, tryRemoveDuplicates | |
| do | handleEvents | |
| elementAt | output(at:) | |
| empty | Publishers.Empty(completeImmediately: true) | |
| enumerated | ❌ | |
| error | Publishers.Once | Publishers.Once has an initializer that takes an Error |
| filter | filter, tryFilter | |
| first | first, tryFirst | |
| flatMap | flatMap | |
| flatMapFirst | ❌ | |
| flatMapLatest | switchToLatest | |
| from | ❌ | |
| groupBy | ❌ | |
| ifEmpty(default:) | replaceEmpty(with:) | |
| ifEmpty(switchTo:) | ❌ | Could be achieved with composition - replaceEmpty(with: publisher).switchToLatest() |
| ignoreElements | ignoreOutput | |
| interval | ❌ | |
| just | Publishers.Just | |
| map | map, tryMap | |
| materialize | ❌ | |
| merge | merge, tryMerge | |
| multicast | multicast | |
| never | Publishers.Empty(completeImmediately: false) | |
| observeOn | receive(on:) | |
| of | ❌ | |
| publish | makeConnectable | |
| range | ❌ | |
| reduce | reduce, tryReduce | |
| refCount | autoconnect | |
| repeatElement | ❌ | |
| retry, retry(3) | retry, retry(3) | |
| retryWhen | ❌ | |
| sample | ❌ | |
| scan | scan, tryScan | |
| share | share | There’s no replay or scope in Combine. Could be “faked” with multicast. |
| skip(3) | dropFirst(3) | |
| skipUntil | drop(untilOutputFrom:) | |
| skipWhile | drop(while:), tryDrop(while:) | |
| startWith | prepend | |
| subscribe | sink | |
| subscribeOn | subscribe(on:) | RxSwift uses Schedulers. Combine uses RunLoop, DispatchQueue, and OperationQueue. |
| takeLast | last | |
| takeUntil | prefix(untilOutputFrom:) | |
| throttle | throttle | |
| timeout | timeout | |
| timer | Timer.publish | |
| toArray() | collect() | |
| window | collect(Publishers.TimeGroupingStrategy) | Combine has a TimeGroupingStrategy.byTimeOrCount that could be used as a window. |
| withLatestFrom | ❌ | |
| zip | zip |
Add any data/operators to the appropriate CSV files in the Data folder, run bundle install and generate.rb.
Finally, commit the changes and submit a Pull Request.