Be Proactive, Use Reactive!

A general overview of reactive programming as presented at CodeMash 2014, with examples in Swift and ReactiveCocoa.

Transcript

1. BE PROACTIVE USE REACTIVE
2. Nutshell.com CodeOptional.com @andrewa2 github.com/andrewsardone (by Kevin Vitale) andrew sardone
3. What is reactive programming?
4. “ ” reactive |rēˈaktiv| … a programming paradigm oriented around data flows and the propagation of change
7. reactive programming data flows propagation of change =
9. we all respond to flowing data and react to changes Model View Controller
10. Cocoa’s KVO? NSNotificationCenter? Ember or Angular observers? Callbacks? Listeners? How is this different from… Programming?
11. Back to the basics
12. Subject Observer notify()
13. DATA STREAMS
14. Data type a value over time
15. •updated property values •mouse cursor position •typing characters into a text field •database records
16. Collection of emitted events ordered in time
17. with functions for observation
18. onNext( ) onComplete()
19. onNext( ) onNext( ) onError() x
20. [ "value”, "other value”, "another value” ] "a value", "other value", "another value"
21. textField.rac_textSignal() .subscribeNext({ (_) -> Void in // value is emitted }, error: { (error) -> Void in // an error occurs within the stream }, completed: { () -> Void in // signal completes successfully })
22. Stream.transform(f: (x) -> y) -> Stream Streams are composable
23. 1 3 2 2 6 4 map { (x) -> Int in x * 2 } Streams are composable
24. 1 2 4 filter { (x) -> Bool in x % 2 == 0 } 4 2 Streams are composable
25. Double tap! Demo
27. taps .bufferWithTime(0.5) .map { ($0 as RACTuple).count } .filter { ($0 as Int) == 2 } .subscribeNext { (_) in println("Double tap!") }
28. taps .bufferWithTime(0.5) .map { ($0 as RACTuple).count } .filter { ($0 as Int) == 2 } .subscribeNext { (_) in println("Double tap!") }
29. taps .bufferWithTime(0.5) .map { ($0 as RACTuple).count } .filter { ($0 as Int) == 2 } .subscribeNext { (_) in println("Double tap!") }
30. 1 2 3 taps .bufferWithTime(0.5) .map { ($0 as RACTuple).count } .filter { ($0 as Int) == 2 } .subscribeNext { (_) in println("Double tap!") }
31. 2 taps .bufferWithTime(0.5) .map { ($0 as RACTuple).count } .filter { ($0 as Int) == 2 } .subscribeNext { (_) in println("Double tap!") }
32. taps .bufferWithTime(0.5) .map { ($0 as RACTuple).count } .filter { ($0 as Int) == 2 } .subscribeNext { (_) in println("Double tap!") } Double tap!
33. RACSignal.combineLatest([ slowToEmitStream, evenSlowerToEmitStream, ]) .doNext { let tuple = $0 as RACTuple processResults( tuple.first, tuple.second) } .subscribeCompleted { () -> Void in println("The work is done!") }
34. MODEL WITH STREAMS
35. MODEL WITH STREAMS BUT…WHY?
36. Claim code should communicate intent
37. Current tooling is insufficient
38. map extension Array { func map<U>(transform: (T) -> U) -> [U] }
39. let input = [1, 2, 3] var output = [Int]() for number in input { output.append(number * 2) } // output: [2, 4, 6] let output = [1, 2, 3].map { $0 * 2 } // output: [2, 4, 6]
40. let input = [1, 2, 3] var output = [Int]() for number in input { output.append(number * 2) } // output: [2, 4, 6] let output = [1, 2, 3].map { $0 * 2 } // output: [2, 4, 6] Concept: 1-1 mapping
41. map reifies 1-1 data transformation
42. Good Thing™ reify |ˈrēəәˌfī| make (something abstract) more concrete or real
43. reactive programming reifies event-driven software
45. var count = 0 upButton.addTarget(self, action: “upButtonTouched:”, forControlEvents: .TouchUpInside) downButton.addTarget(self, action: “downButtonTouched:", forControlEvents: .TouchUpInside) countLabel.text = String(count) func upButtonTouched(sender: UIButton) { count++ countLabel.text = String(count) } func downButtonTouched(sender: UIButton) { count-- countLabel.text = String(count) }
46. let upTaps = upButton .rac_signalForControlEvents(.TouchUpInside) let downTaps = downButton .rac_signalForControlEvents(.TouchUpInside) let count = RACSignal.merge([ RACSignal.return(0), upTaps.mapReplace(1), downTaps.mapReplace(-1) ]) .scanWithStart(0, reduce: { $0 + $1 }) .map { String($0) } count ~> RAC(self, "countLabel.text")
47. client.loginWithSuccess({ client.loadCachedTweetsWithSuccess({ (tweets) in client.fetchTweetsAfterTweet(tweets.last, success: { (tweets) -> Void in // Now we can show our tweets }, failure: { (error) -> Void in presentError(error) }) }, failure: { (error) -> Void in presentError(error) }) }, failure: { (error) -> Void in presentError(error) })
48. client.login() .then { return client.loadCachedTweets() } .flattenMap { (tweets) -> RACStream! in return client.fetchTweetsAfterTweet(tweets.last) } .subscribeError({ (error) -> Void in presentError(error) }, completed: { () -> Void in // Now we can show our tweets })
49. func loginWithSuccess( success: () -> Void, failure: (NSError) -> Void) { // function doesn’t return anything // it jumps into two callbacks based on return } func login() -> RACSignal { // function has a native return value // a data stream object that we can observe }
50. SO… HOW DO I DO THIS?
51. ReactiveCocoa ReactiveExtensions RxJava Bacon.js Elm github.com/ReactiveCocoa/ReactiveCocoa github.com/Reactive-Extensions github.com/ReactiveX/RxJava github.com/baconjs/bacon.js elm-lang.org
52. SOURCES FURTHER READING
53. Missing RX Intro Input & Output RxMarbles Other j.mp/missingrxintro j.mp/joshaberio rxmarbles.com pinboard.in/u:andrewsardone/t:reactive
54. B Y E (photo by Chris Dzombak) (puppy by Shane Bliemaster)