Let's be functional-reactive in Cocoa world

Slides from talk on MO Conf 2016
mo.dev.by

Transcript

1. Let’s be functional-reactive in Cocoa world
2. About me iOS developer at YOTA Official member of Typhoon framework vasilenkoigor i_vasilenko igorvasilenko.me
3. Agenda FRP explained ReactiveCocoa explained Practice with RAC RAC vs. RxSwift Conclusion
4. Agenda FRP explained ReactiveCocoa explained Practice with RAC RAC vs. RxSwift Conclusion
5. FRP explained
6. FRP explained «Is a programming paradigm for reactive programming using the building blocks of functional programming.» - Wikipedia
8. FRP explained #BULLSHIT
9. FRP explained • Reactive programming is programming with asynchronous data streams • Amazing toolbox of functions to combine, create and filter any of those streams Let’s cut the bullshit
10. x: 10 x: 20 x: 30 x: 40 x: 50 Data stream
11. FRP explained • Reactive programming is programming with asynchronous data streams • Amazing toolbox of functions to combine, create and filter any of those streams Let’s cut the bullshit
12. FRP explained Why should you consider adopting RP? • Code will likely be more concise • Efficiency • Architecture • Hot-swapping • Binding
13. Agenda FRP explained ReactiveCocoa explained Practice with RAC RAC vs. RxSwift Conclusion
14. Agenda FRP explained ReactiveCocoa explained Practice with RAC RAC vs. RxSwift Conclusion
15. ReactiveCocoa explained
16. ReactiveCocoa explained • ReactiveCocoa (RAC) is a framework developed by GitHub • ReactiveCocoa is an implementation FRP on iOS/macOS • Currently framework version - 4.2.1
17. ReactiveCocoa explained Signals Signal is an object that can emit Events.
18. ReactiveCocoa explained Signals public final class Signal<Value, Error: ErrorType>
19. ReactiveCocoa explained Signals let mySignal = Signal<Int, NSError>({ observer in observer.sendNext(1) observer.sendNext(2) /* send other events to observer */ return nil })
20. ReactiveCocoa explained Events There are four types of events that a signal can emit
21. ReactiveCocoa explained Events Next(Value) events are most common ones. They carry a certain value;
22. ReactiveCocoa explained Events Completed event signals the successful completion of a signal;
23. ReactiveCocoa explained Events Failed(Error) event carries an error object that reflects the reason of failed signal completion;
24. ReactiveCocoa explained Events Interrupted is a termination event that signifies neither a successful, nor failed completion of a signal.
25. ReactiveCocoa explained Timeline of Events /^Next*(Failed|Completed|Interrupted)?$/
26. ReactiveCocoa explained Observers You can think of observers as functions that do something with event when it arrives.
27. ReactiveCocoa explained Observers • observeNext: observe only Next events carrying a value • observeFailed: observe only Failed event that carry an error object • observeCompleted: observe only signal completion event
28. ReactiveCocoa explained Pipes In the days of RAC 2.x this used to be represented by RACSubject class instances. let (signal, observer) = Signal<Int, NSError>.pipe()
29. ReactiveCocoa explained Pipes signal.observeNext({ print($0)}) observer.sendNext(0) // prints "0" observer.sendNext(1) // prints "1"
30. ReactiveCocoa explained Operators map: changes function from one type to another or modifies the value retaining the type someSignal.map { (intValue) -> String in return "value: \(intValue)" }
31. ReactiveCocoa explained Operators filter: forwards only the values that pass a given predicate closure;
 someSignal.filter { (intValue) -> Bool in return intValue > 0 }
32. ReactiveCocoa explained Operators take: takes up to N values sent by the signal someSignal.take(1).observeNext { (intValue) in // Next event will be once received }
33. ReactiveCocoa explained Operators throttle: sends new signal’s values no more often than provided time interval someSignal.throttle(30,onScheduler:UIScheduler())
34. ReactiveCocoa explained Operators let combineSignals = combineLatest(numbersSignal,lettersSignal) .on { (intValue, stringValue) in print(intValue) print(stringValue) } combineLatest: a free function that combines values from variable number of signals
35. ReactiveCocoa explained Operators combineSignals.reduce("", { (startValue, valuesTuple) in return valuesTuple.1 }).observeNext { (stringValue) in print(stringValue) } reduce: upon signal completion combines all sent values using provided function

36. ReactiveCocoa explained SignalProducers You’d want a pull-driven stream of events so that you could receive events on demand.
37. ReactiveCocoa explained SignalProducers SignalProducer <String, NSError> {(observer, disposable) in /// some task (api request, saving to database, etc.) }
38. ReactiveCocoa explained SignalProducers Another big difference of the SignalProducer is that it can contain side-effects.
39. ReactiveCocoa explained SignalProducers producer.on(started: { /// Some work }, event: { (event) in /// Some work }) other side-effects: failed, interrupted, completed, terminated, disposed

40. ReactiveCocoa explained MutableProperty Mutable property is a concrete implementation of read-write property and is probably mostly used type among other ones. var bankAccountBalance = MutableProperty<Double>(100)
41. ReactiveCocoa explained MutableProperty bankAccountBalance.value = 200; bankAccountBalance.signal.observeNext { (value) in /// Some work } Observe and change value
42. ReactiveCocoa explained Schedulers When receiving a signal or producer from unknown code, it can be difficult to know which thread events will arrive upon.
43. ReactiveCocoa explained Schedulers someSignal.observeOn(UIScheduler()).observeNext { (value) in /// observe on Main Thread } Whenever such a guarantee is important, the observeOn operator should be used to force events to be received upon a specific scheduler.
44. ReactiveCocoa explained Schedulers Schedulers are similar to Grand Central Dispatch queues, but schedulers support cancellation (via disposables), and always execute serially.
45. Agenda FRP explained ReactiveCocoa explained Practice with RAC RAC vs. RxSwift Conclusion
46. Agenda FRP explained ReactiveCocoa explained Practice with RAC RAC vs. RxSwift Conclusion
47. Practice with RAC github.com/vasilenkoigor/MOConf2016Practice
48. Agenda FRP explained ReactiveCocoa explained Practice with RAC RAC vs. RxSwift Conclusion
49. Agenda FRP explained ReactiveCocoa explained Practice with RAC RAC vs. RxSwift Conclusion
50. RAC vs. RxSwift
51. RAC vs. RxSwift • ReactiveX - a group which created a common API for FRP implementations • RxSwift is a relatively recent addition to ReactiveX • Currently framework version - 2.6.0
52. RAC vs. RxSwift Hot and cold RxSwift doesn’t support differentiate between hot and cold signals Observable <String>.just("Say hello RxSwift")
53. RAC vs. RxSwift Error handling RxSwift doesn’t support parameterized type for the error case Observable <T>
54. RAC vs. RxSwift UI bindings • RxSwift bindings are a joy to use • ReactiveCocoa bindings only with custom extensions
55. RAC vs. RxSwift RAC in big projects? • WhatsApp • Github • Yota • Yandex • SoundCloud
56. RAC vs. RxSwift Why YOTA using ReactiveCocoa? • We want to be able to better describe our system • We want having different types to differentiate between hot and cold signals • We want a battle tested framework, used by many people, in many projects
57. Agenda FRP explained ReactiveCocoa explained Practice with RAC RAC vs. RxSwift Conclusion
58. Agenda FRP explained ReactiveCocoa explained Practice with RAC RAC vs. RxSwift Conclusion
59. Thank you! <3