ReactiveCocoa

A brief overview of reactive programming and how it is applied to Objective C.

Transcript

3. OVERVIEW ⇁  FUNCTIONAL REACTIVE PROGRAMMING ⇁  REACTIVECOCOA* ⇁  RESPONDER / CALLHANDLE? ⇁  CODE EXAMPLES
4. REACTIVECOCOA* TOPICS ⇁  BUILDING BLOCKS ⇁  COLLECTION TRANSFORMATION ⇁  ASYNCHRONOUS PROGRAMMING ⇁  COMPOSITION & PARALLELIZATION ⇁  DATA BINDING & MVVM
5. FUNCTIONAL REACTIVE PROGRAMMING First look at
6. FRP ❝FRP IS A HIGH-LEVEL WAY TO WORK WITH INTERACTIONS. IT PROVIDES CONTROL FLOW STRUCTURES FOR TIME. IT IS BUILT AROUND THE IDEA OF TIME-VARYING VALUES, CALLED SIGNALS. ❞ — elm-lang.org
7. ٩۹(๏̯͡๏)ゞ? WAIT. WHAT?!
8. FRP ❝REPRESENT & QUERY ASYNCHRONOUS DATA STREAMS, AND PARAMETERIZE THE CONCURRENCY IN THE ASYNCHRONOUS DATA STREAMS USING SCHEDULERS.❞ — rx.codeplex.com
9. FUNCTIONAL REACTIVE INPUT ⤑ OUTPUT AVOID STATE AVOID MUTABLE DATA NO SIDE-EFFECTS DECLARATIVE
10. FUNCTIONAL REACTIVE DATA FLOW CHANGE PROPAGATION SIDE-EFFECTS EVENTS NON-BLOCKING COMPOSITION
11. (-_-)ゞ
14. DIFFERENT PARADIGM NOT JUST A LIBRARY
15. PROCEDURAL (HOW?)
16. RISE OF FRP
17. ERIK MEIJER ⇁  FUNCTIONAL PROGRAMMING & COMPILER IMPLEMENTATION ⇁  MICROSOFT (2000 – 2013) ⇁ REACTIVE EXTENSIONS (RX) FOR C#/.NET
18. WHAT’S THE DIFFERENCE BETWEEN
19. NOTHING.
20. BOTH ARE JUST
21. DB EXAMPLE [[[[db getArticles] filter:^BOOL(Article* article) { return article.isDraft; }] map:^Draft*(Article* article) { Draft *draft = [Draft new]; draft.title = article.title; return draft; }] doNext:^(Draft *draft) { // Do something with each draft }];
22. TOUCH EXAMPLE [[[[view touchSignals] filter:^BOOL(UITouch* touch) { return touch.duration > 100; }] map:^TouchPoint*(UITouch* touch) { TouchPoint* tp = [TouchPoint new]; tp.x = touch.x; tp.y = touch.y; return tp; }] doNext:^(TouchPoint *tp) { // Do something with each tp }];
23. RX.NET REACTIVECOCOA RXJAVA* RXJS RXCPP RXPY RXRB BACONJS
24. FRP IN DESIGN PATTERNS 3-in-1
25. IENUMERATOR<T> ⇁  ENUMERABLE<T> bool MoveNext()
26. IOBSERVER<T> void OnCompleted() void OnError() void OnNext() OBSERVABLE<T> Disposable subscribe(Observer<T>)
27. DISPOSABLE void dispose()
28. SIGNAL IENUMERATOR<T> IOBSERVER<T> ENUMERABLE<T> DISPOSABLE OBSERVABLE<T>
29. REACTIVECOCOA Building Blocks
30. STREAM ⇁  ABSTRACT BASE TYPE ⇁  ANY SERIES OF OBJECT VALUES ⇁  VALUES AVAILABLE NOW OR IN FUTURE RACStream
31. SIGNAL ⇁  PUSH-DRIVEN STREAM ⇁  DATA TO BE DELIVERED IN THE FUTURE ⇁  VALUES SENT AS THEY ‘ARRIVE’ RACSignal A B
32. ⇁  SUBSCRIBE TO RECEIVE EVENTS ⇁  SENDS 3 EVENT TYPES ⇁ ‘NEXT’ ⇁ ‘ERROR’ ⇁ ‘COMPLETE’ ⇁  IMMUTABLE A B
33. COLD ⇁  DEFAULT ⇁  START WORK WITH EACH NEW SUBSCRIPTION RACSignal HOT ⇁  WORK STARTS ONCE ⇁  FOR ALL SUBSCRIPTIONS RACMultiCastConnection
34. SIDE-EFFECTS ⇁  WORK THAT HAPPENS AS SIGNALS MOVE THROUGH ⇁  NEXT ⇁  ERROR ⇁  COMPLETE ⇁  UI ⇁  FIRING OTHER SIGNALS ⇁ …
35. SEQUENCE ⇁  PULL-DRIVEN STREAM ⇁  DATA ALREADY AVAILABLE ⇁  VALUES REQUESTED LAZILY RACSequence
36. SUBJECT ⇁  INHERITS FROM SIGNAL ⇁  MUTABLE ⇁  ‘NEXT’, ‘ERROR’, ‘COMPLETE’ EVENTS FROM OUTSIDE ⇁  BRIDGE NON-REACTIVE CODE RACSubject
37. SUBSCRIPTION ⇁  WAITS FOR EVENTS FROM A SIGNAL ⇁  DISPOSED WHEN SIGNAL COMPLETES/ERRORS id<RACSubscriber>
38. DISPOSABLE ⇁  CANCELLATION & RESOURCE CLEANUP ⇁  UNSUBSCRIBES FROM SIGNALS ⇁  IMPLICIT OR EXPLICIT ⇁  RESULT OF A SUBSCRIPTION RACDisposable
39. SCHEDULER ⇁ (SERIAL) EXECUTION QUEUE FOR SIGNALS ⇁  SIMILAR TO THREADS ⇁  SUPPORTS CANCELLATION ⇁  NO SYNCHRONOUS EXECUTION ⇁  PREVENTS DEADLOCKS RACScheduler
40. ⇁  CREATES & SUBSCRIBES TO A SIGNAL ⇁  IN RESPONSE TO UI ACTION ⇁  TYPICAL USES ⇁  HANDLERS ⇁  VIEWMODELS COMMAND RACCommand
41. BUTTON TAP SVC CALL FILTER MAP ARRAY à UI FLATTENMAP FILTER
42. SIGNAL OPERATIONS ⇁ -CONCAT: ⇁ -MERGE: ⇁ -FLATTENMAP: ⇁ -THEN:
43. SIGNAL OPERATIONS ⇁ -RETRY: ⇁ -IF:THEN:ELSE ⇁ -DELAY: ⇁ -THROTTLE: ⇁ -TAKE: ⇁ -TRY:CATCH: ⇁ +RETURN: operators  
44. COLLECTION TRANSFORMATION
45. COLLECTION TRANSFORMATION ⇁  HIGHER ORDER FUNCTIONS ⇁  MAP ⇁  FILTER ⇁  FOLD ⇁  REDUCE
46. EXAMPLE NSArray *got = @[@”Tyrion”, @”Jaime”, @”Daenerys”, @”Jon”]; NSMutableArray *gotPeople = [[NSMutableArray alloc] init]; for(NSString *name in got) { if([name hasPrefix:@”J”]) { continue; } Person *p = [Person new]; p.name = name; [gotPeople addObject:p] }
47. EXAMPLE NSArray *got = @[@”Tyrion”, @”Jaime”, @”Daenerys”, @”Jon”]; [[got.rac_sequence filter:^BOOL(NSString *name) { return [name hasPrefix:@”J”]; }] map:^Person*(NSString *name) { Person *p = [Person new]; p.name = name; return p; }];
48. ASYNCHRONOUS PROGRAMMING
49. MODELS ⇁  EVENT-DRIVEN / CALLBACK-BASED ⇁  INTERRUPTS FLOW ⇁  NESTING = PROBLEMATIC ⇁  FUTURES / PROMISES ⇁  ENCAPSULATES SUCCESS / FAILURE HANDLERS ⇁  SOME SEQUENCING & PARALLELISM ⇁  BOTH: REPRESENT SINGLE VALUES
50. SIGNALS ⇁  LINEAR FLOW (LIMITED NESTING) ⇁  ENCAPSULATES STREAM OF VALUES OVER TIME ⇁  INFINITELY COMPOSABLE ⇁  SIMPLIFIED SEQUENCING & PARALLELIZATION ⇁  SERIAL QUEUE
51. EXAMPLE [[[[[self.service getUpcomingMeetings] collect] doNext:^(NSArray *upcomingMeetings) { self.upcomingMeetings = upcomingMeetings; }] doError:^(NSError *error) { [[AlertView alertWithError:error] show]; }] subscribeCompleted:^{ [self.tableView reloadData]; }];
52. EXAMPLE [[[[[self.service getUpcomingMeetings] collect] doNext:^(NSArray *upcomingMeetings) { self.upcomingMeetings = upcomingMeetings; }] doError:^(NSError *error) { [[AlertView alertWithError:error] show]; }] subscribeCompleted:^{ [self.tableView reloadData]; }]; SIGNAL   SUBSCRIPTION   SIDE-­‐EFFECT   SIDE-­‐EFFECT   OPERATION   (return)  DISPOSABLE  
53. COMPOSITION & PARALLELIZATION
54. COMPOSITION ⇁  DEPENDENT TASKS ⇁  E.G. NETWORK REQUESTS ⇁  SIGNAL CHAINING ⇁  NESTING
55. COMPOSITION – EXAMPLE [client logInWithSuccess:^{ [client loadCachedMessagesWithSuccess:^(NSArray *messages) { [client fetchMessagesAfterMessage:messages.lastObject success:^(NSArray *nextMessages) { NSLog(@"Fetched all messages."); } failure:^(NSError *error) { [self presentError:error]; }]; } failure:^(NSError *error) { [self presentError:error]; }]; } failure:^(NSError *error) { [self presentError:error]; }];
56. COMPOSITION – EXAMPLE [[[[client logIn] then:^{ return [client loadCachedMessages]; }] flattenMap:^(NSArray *messages) { return [client fetchMessages:messages.lastObject]; }] subscribeError:^(NSError *error) { [self presentError:error]; } completed:^{ NSLog(@"Fetched all messages."); }];
57. PARALLELIZATION ⇁  ONE-BY-ONE ⇁ [RACSignal -concat:@[signals ]] ⇁  IN PARALLEL ⇁ [RACSignal -combineLatest:@[signals ]] ⇁  RETURN TYPES? JUST SIGNALS.
58. DATA BINDING & MVVM ReactiveCocoa
59. DATA BINDING ⇁  NON-STANDARD ON IOS ⇁  REPLACEMENT FOR KEY-VALUE OBSERVING (KVO) ⇁  TURNS REGULAR PROPERTIES INTO SIGNALS
60. DATA BINDING [[RACObserve(self, username) filter:^(NSString *newName) { return [newName hasPrefix:@"j"]; }] subscribeNext:^(NSString *newName) { NSLog(@"%@", newName); }];
61. MVVM VIEW VIEWMODEL MODEL NOTIFIES   COMMANDS   REFERENCES  
62. RESPONDER / CALLHANDLE ?
63. CODE EXAMPLES