ReactiveCocoa at MobiDevDay 2013

https://github.com/andrewsardone/RACMobiDevDay
Recording: https://vimeo.com/65637501

These are the slides from my MobiDevDay 2013 talk on ReactiveCocoa.

ReactiveCocoa (RAC) is an Objective-C framework for Functional Reactive Programming. It builds off of Cocoa's own key-value observing mechanism to provide a high-level, declarative API for composing operations on streams of data, state, and asynchronous tasks. What does all of that mean? We'll find out as we explore RAC's potential for helping us better reason about the creation of our apps.

Also included in the Declarative Programming section is https://github.com/mneorr/ObjectiveSugar

Additional resources:

https://github.com/ReactiveCocoa
https://pinboard.in/u:andrewsardone/t:ReactiveCocoa
https://github.com/andrewsardone/RACMobiDevDay
http://nsbrief.com/81-justin-spahr-summers/
http://j.mp/joshaberio
http://j.mp/reactiveextensions

Transcript

1. ReactiveCocoa or: How I Learned to Stop Worrying and Learn FRP
2. Abstraction
3. Objective-C OOP #import <Foundation/Foundation.h> @interface Person : NSObject @property (nonatomic, copy) NSString *name; - (void)say:(NSString *)message withExclaim:(BOOL)exclaim; @end @implementation Person - (void)say:(NSString *)message withExclaim:(BOOL)exclaim { if (exclaim) { message = [message uppercaseString]; } NSLog(@"%@", message); } @end
4. Declarative Programming
5. NSArray *array = @[@"foo", @"bar", @"baz"]; NSMutableArray *uppercaseArray = [NSMutableArray array]; for (int i = 0; i < array.count; i++ ) { uppercaseArray[i] = [array[i] uppercaseString]; } // uppercaseArray: @[ @"FOO", @"BAR", @"BAZ" ] id u = [@[@"foo", @"bar", @"baz"] map:^id(NSString *s) { return [s uppercaseString]; }]; // u: @[ @"FOO", @"BAR", @"BAZ" ] Describes how to compute Describes what to compute
6. Declarative Programming = Good thing
7. The State of Our Apps
8. Lots of state Poor code locality Boilerplate
9. Complexity
10. Taps Keyboard events GPS events Web service responses … UI updates File on disk New DB record Web service request … INPUT w!r" I#p$% &#' O$%p$% by Josh Abernathy http://j.mp/joshaberio OUTPUT
11. Is there a better abstraction?
12. Reactive Programming “Programming around data flows and the propagation of change”
13. a = 2 b = 2 c = a + b # c is 4 b = 3 # now what’s the value of c?
15. Data types that represent a value over time
16. Streams sequences of values over time Signals observable streams affords reaction to past, present, and future values
17. a := 2 # signal b := 2 # signal c := a + b # signal binding # other signals b 2 3 c a + b 4 5 2 a 4 7 5 6 1
18. ReactiveCocoa “A [Cocoa] framework for composing and transforming streams of values”
19. KVO property UI events Network request Async work … Values over time https://speakerdeck.com/joshaber/reactivecocoa-for-a-better-world
20. @interface RACSignal : RACStream [RACAble(self.username) subscribeNext:^(NSString *newName) { NSLog(@"%@", newName); }]; https://github.com/ReactiveCocoa/ReactiveCocoa/blob/master/README.md next completed error sending a single value done sending all values & successful sending values but terminated in error
21. [self.textField.rac_textSignal subscribeNext:^(NSString *text) { NSLog(@"Incoming text signal: %@", text); }];
22. [[self.textField.rac_textSignal map:^id(id text) { return [text stringByAppendingString:@" – map'd it"]; }] subscribeNext:^(NSString *text) { NSLog(@"Incoming text signal: %@", text); }];
23. RACSignal *url = [[[[button rac_signalForControlEvents:UIControlEventTouchUpInside] map:^id(id _) { return NSString *s = [@[ [NSURL URLWithString:@"http://nutshell.com"], [NSURL URLWithString:@"http://google.com"], [NSURL URLWithString:@"http://wikipedia.org"], [NSURL URLWithString:@"http://apple.com"], [NSURL URLWithString:@"http://github.com/ReactiveCocoa/ReactiveCocoa"], ] aps_randomObject]; }] publish] autoconnect]; RACSignal *html = [[url flattenMap:^RACStream *(NSURL *url) { NSStringEncoding encoding = NSUTF8StringEncoding; return [NSString rac_readContentsOfURL:url usedEncoding:&encoding scheduler:[RACScheduler scheduler]; }] deliverOn:RACScheduler.mainThreadScheduler]; RAC(label, text) = [url map:^id(NSURL *u) { return u.absoluteString; }]; [webView rac_liftSelector:@selector(loadHTMLString:baseURL:) withObjects:html, url];
24. field.enabled = NO; [worker doWorkWithCompletionBlock:^(id result, NSError *error) { field.enabled = YES; if (error) { /* handle error */ } else /* handle result */ }]; RACCommand *doWork = [worker doWorkAsCommand]; RAC(field, enabled) = [RACAble(doWork, executing) not]; // later, when we want to do the work // our UI pipes are plugged together so we don’t need to // worry about that [doWork execute:sender]; // handle result of doWork somewhere else where it matters … less imperative … more declarative
25. Demo
82. Reduce unnecessary state Better code locality Fluent interface Simple data structures Composing functions
83. Thanks!
84. Andrew Sardone twitter: @andrewa2 app.net: @andrewsardone github.com/andrewsardone github.com/ReactiveCocoa pinboard.in/u:andrewsardone/t:ReactiveCocoa github.com/andrewsardone/RACMobiDevDay nsbrief.com/81-justin-spahr-summers/ Input and Output – j.mp/joshaberio Reactive Extensions (Rx) – j.mp/reactiveextensions