reactiveswift-to-combine-cheatsheet
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Published
20 hours ago •
Fueled
Fueled
A list ReactiveSwift classes and operators with their equivalent for Combine
A Cheat Sheet of various equivalent of ReactiveSwift for Combine.
This list is by no mean exhaustive, and while each Combine equivalent try to have the same semantic as its ReactiveSwift, there might be cases where the behavior differs in subtle manners.
Please do report these cases so we can update the list accordingly.
Basics
| ReactiveSwift | Combine | |
|---|---|---|
| Platforms supported | • iOS 8.0+ • macOS 10.9+ • Mac Catalyst 13.0+ • watchOS 2.0+ • tvOS 9.0+ • Linux |
• iOS 13.0+ • macOS 10.15+ • Mac Catalyst 13.0+ • watchOS 6.0+ • tvOS 13.0+ |
| Framework Consumption | Third-party | First-party (built-in) |
| Maintained by | Open-Source / Community | Apple |
| UI Bindings | ReactiveCocoa (interfacing with UIKit) | SwiftUI[1] |
[1] Is actually a full UI framework replacing UIKit, that natively supports Combine.
Components
Note that in Combine, anything can be transformed in an AnyPublisher through eraseToAnyPublisher().
This means that all the equivalent given for Combine can be returned as an AnyPublisher.
Core
| ReactiveSwift | Combine | Notes |
|---|---|---|
SignalProducer |
Deferred<PassthroughSubject> |
|
Signal |
Publisher |
|
Signal.pipe() |
PassthroughSubject |
|
Property |
private(set) variable annotated with @Published (use $variable to get the underlying publisher) |
|
MutableProperty |
CurrentValueSubject, or a variable annotated with @Published (use the $variable to get the underlying publisher) |
|
ValidatingProperty |
❌ | |
Action |
❌ | An equivalent exists at https://github.com/Fueled/ios-utilities/blob/v3-support/FueledUtils/Combine/Action.swift |
Disposable |
Cancellable |
|
SerialDisposable |
❌ | No direct equivalent, see ScopedDisposable<SerialDisposable> |
CompositeDisposable |
❌ | No direct equivalent, see ScopedDisposable<CompositeDisposable> |
Event |
❌ | No direct equivalent |
Lifetime |
❌ | |
Observer |
Subscriber |
AnySubscriber can be used to create a Subscriber without creating a type that conforms to the former |
Scheduler |
Scheduler |
DispatchQueue, RunLoop, ImmediateScheduler, OperationQueue conforms to Scheduler |
DateScheduler |
Scheduler |
|
Atomic |
❌ | An equivalent called AtomicValue exists at https://github.com/Fueled/ios-utilities/blob/v3-support/FueledUtils/Core/Atomic.swift#L19-L46 |
Bag |
❌ |
Other
| ReactiveSwift | Combine | Notes |
|---|---|---|
SignalProducer<Value, Failure>(value: value) |
Just(value).setFailureType(Failure.self) |
|
SignalProducer<Value, Failure>(error: error) |
Fail(outputType: Value.self, failure: error) |
|
SignalProducer<Value, Failure>.empty |
Empty().setFailureType(Failure.self) |
|
SignalProducer<Value, Failure>.never |
Empty(completeImmediately: false).setFailureType(Failure.self) |
|
Signal<Value, Failure>.empty |
Empty().setFailureType(Failure.self) |
|
Signal<Value, Failure>.never |
Empty(completeImmediately: false).setFailureType(Failure.self) |
|
Property<Value>(value: value) |
Just(value).setFailureType(Failure.self) |
|
ScopedDisposable<SerialDisposable> |
AnyCancellable |
|
ScopedDisposable<CompositeDisposable> |
Collection of AnyCancellables |
Call anyCancellable.store(in: collection), where collection can be an Array, a Set, or any other RangeReplaceableCollection |
Operators
| ReactiveSwift | Combine | Notes |
|---|---|---|
combineLatest() |
Publishers.CombineLatest/Publishers.CombineLatest3/Publishers.CombineLatest4 |
Limited to up to 4 parameters, as opposed to 10 for ReactiveSwift. |
flatMap(.merge) { <...> } |
flatMap { <...> } |
|
flatMap(.latest) { <...> } |
map { <...> }.switchToLatest() |
|
mapError |
mapError |
|
flatMapError |
catch |
|
zip |
Publishers.zip/Publishers.zip2/Publishers.zip3 |
|
merge(one, two, ..., eight) |
Publishers.Merge/Publishers.Merge2/.../Publishers.Merge8 |
|
merge([]) |
Publishers.MergeMany |
|
start() |
self.sink(receiveCompletion: { _ in }, receiveValue: { _ in }) |
|
startWithValues { value in <...> } |
self.sink(receiveValue: { value in <...> }) |
|
startWithResult { result in <...> } |
self.sink(receiveCompletion { completion in if case .failure(let error) = completion { <...> } }, receiveValue: { value in <...> }) |
|
ignoreError() |
self.catch { _ in Empty() } |
|
skipNil() |
❌ | An equivalent can be found at https://github.com/Fueled/ios-utilities/blob/v3-support/FueledUtils/Combine/PublisherExtensions.swift#L36-L38 |
skip(first:) |
dropFirst() |
|
skip(until:) |
drop(untilOutputFrom:) |
|
skip(while:) |
drop(while:) |
|
scan() |
scan() |
|
throttle() |
throttle() |
|
SignalProducer<Date, Never>.timer() |
Timer.publish().autoconnect() |
|
prefix() |
prepend() |
|
on() |
handleEvents() |
|
<~ |
If binding to a property on an class, can use .assign(to:, on:). Keep in mind that this will retain the object. |
|
compositeDisposable += <disposable> |
store(in: &cancellables) |
Format inspired by https://github.com/CombineCommunity/rxswift-to-combine-cheatsheet
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