Objective-C on Lambdas

Intro to functional & reactive programming with some ReactiveCocoa for Objective-C (revision 3, Feb 27 2014 specially for CocoaHeads Krakow)

Video (in Russian): http://vimeo.com/79623400

Transcript

2. ƛavericks @darkproger
3. Functional Programming with Objective-C
4. Objective-C (the good parts) Static typing Dynamic binding Blocks ARC
5. Objective-C (really) Boring Verbose Low-level OOP
6. -[NSBitmapImageRep initWithBitmapDataPlanes:(unsigned char **)planes pixelsWide:(NSInteger)width pixelsHigh:(NSInteger)height bitsPerSample:(NSInteger)bps samplesPerPixel:(NSInteger)spp hasAlpha:(BOOL)alpha isPlanar:(BOOL)isPlanar colorSpaceName:(NSString *)colorSpaceName bitmapFormat:(NSBitmapFormat)bitmapFormat bytesPerRow:(NSInteger)rowBytes bitsPerPixel:(NSInteger)pixelBits]; AppKit
7. [headerView addConstraint:[NSLayoutConstraint constraintWithItem:excessivelyBigView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationLessThanOrEqual toItem:headerView attribute:NSLayoutAttributeHeight multiplier:0.0 constant:45]]; AutoLayout
8. - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { if ([keyPath isEqualToString:@"state"]) { /* ... */ } } KVO
9. NSMutableArray *result = [NSMutableArray arrayWithCapacity:mutableOperations.count]; [mutableOperations enumerateObjectsUsingBlock:^(AFHTTPRequestOperation *op, NSUInteger idx, BOOL *stop) { [result addObject:change_op(op)]; }]; return result;
10. NSMutableArray *result = [NSMutableArray arrayWithCapacity:mutableOperations.count]; [mutableOperations enumerateObjectsUsingBlock:^(AFHTTPRequestOperation *op, NSUInteger idx, BOOL *stop) { [result addObject:change_op(op)]; }]; return result; state change state return state!
11. NSMutableArray *result = [NSMutableArray arrayWithCapacity:mutableOperations.count]; [mutableOperations enumerateObjectsUsingBlock:^(AFHTTPRequestOperation *op, NSUInteger idx, BOOL *stop) { [result addObject:change_op(op)]; }]; return result; state change state return state! also, way too much code. Check AFIncrementalStore
12. 68: if (isDataRetrieved == NO) { 86: if(line.Id == tripId){ 110: if([[Config ArrPsgWaitingTrips] count]+[[Config ArrPsgPastTrips] count] > 0) 120: if([[Config ArrPsgWaitingTrips] count]+[[Config ArrPsgPastTrips] count] > 0) 133: if([[Config ArrPsgWaitingTrips] count]+[[Config ArrPsgPastTrips] count] == 0) 163: if (aTrip.Id == pushedTrip.Id) { 189: if (line.Id == aTrip.Id) { 197: if (isFound == NO) { 200: if (line.Id == aTrip.Id) { 214: if (isFound == YES) { +
13. 68: if (isDataRetrieved == NO) { 86: if(line.Id == tripId){ 110: if([[Config ArrPsgWaitingTrips] count]+[[Config ArrPsgPastTrips] count] > 0) 120: if([[Config ArrPsgWaitingTrips] count]+[[Config ArrPsgPastTrips] count] > 0) 133: if([[Config ArrPsgWaitingTrips] count]+[[Config ArrPsgPastTrips] count] == 0) 163: if (aTrip.Id == pushedTrip.Id) { 189: if (line.Id == aTrip.Id) { 197: if (isFound == NO) { 200: if (line.Id == aTrip.Id) { 214: if (isFound == YES) { + state? state? state? state? state? state?
14. …state?
16. you ok? you good? you need anything? you sure you’re fine? argh!!
17. you ok? you good? you need anything? you sure you’re fine? argh!!
18. you ok? you good? you need anything? you sure you’re fine? argh!! STATE SUCKS!
19. singletons too (dispatch_once story here)
20. Functional no state!
21. Functional HOFs
22. Functional HOFs HOFs > OOP patterns
23. Functional immutable data no side effects .. thread-safe
24. Functional simple
26. > let numbers = [1,2,3,4,5] > map (+1) numbers [2,3,4,5,6] > filter even numbers [2,4] > foldl1 (+) numbers 15 > sum numbers 15 > zip numbers numbers [(1,1),(2,2),(3,3),(4,4),(5,5)]
27. Functional declarative rather than imperative
28. NSMutableArray
29. NSArray
30. NSArray *newMaps = [maps map:^id(CXMap *map) { return [map changeSomehow]; }]; http://underscorem.org/ https://github.com/mogeneration/functionalkit and more!
31. NSArray *newMaps = [maps map:^id(CXMap *map) { return [map changeSomehow]; }]; entirely new array! mapping function (HOF) returns a new object
32. Function Composition
34. > let numbers = [1,2,3,4,5] > map (+1) numbers [2,3,4,5,6] > filter even numbers [2,4] > foldl1 (+) numbers 15 > sum numbers 15
35. > let numbers = [1,2,3,4,5] > map (+1) numbers [2,3,4,5,6] > filter even numbers [2,4] > foldl1 (+) numbers 15 > sum numbers 15 ! ! > foldl1 (+) . filter even . map (+1) $ numbers 12
36. > let numbers = [1,2,3,4,5] > map (+1) numbers [2,3,4,5,6] > filter even numbers [2,4] > foldl1 (+) numbers 15 > sum numbers 15 ! ! > foldl1 (+) . filter even . map (+1) $ numbers 12 composition ^ composition ^
37. > let f = foldl1 (+) . filter even . map (+1) > :type f f :: [Integer] -> Integer > f numbers 12 int f(int array[])
38. > let f = foldl1 (+) . filter even . map (+1) > :type f f :: [Integer] -> Integer > f numbers 12 int f(int array[]) NSInvocation a block
39. Functors http://adit.io/posts/2013-04-17-functors,_applicatives,_and_monads_in_pictures.html
41. > let numbers = [1,2,3,4,5] > fmap (+1) numbers [2,3,4,5,6] ! > fmap (+1) (Just 2) Just 3
44. Concurrency
45. [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]; }];
46. -> * login * load data from cache * load data from network * send stats
47. report_stats( load_network( load_cached( login(user)))
48. dashboard = login . load_cache . load_network . report_stats
49. scripts != apps
50. Objective-C
    concurrency -scheduleInRunLoop:
51. Objective-C
    concurrency NSThread @synchronized
52. Objective-C
    advanced
    concurrency dispatch(3)
54. Qs! units of work NSRunLoop dispatch_queue NSOperationQueue
55. Qs! actors (queues associated with an execution context) ! -performSelector: https://code.google.com/p/plankton-platform/ https://code.google.com/p/plactorkit/
58. true for motivational training losers different story in (user-oriented) programming
59. ReactiveCocoa
60. pod 'ReactiveCocoa', '~> 2.1.3'
61. - self.title = [map name]; + RAC(self, title) = RACObserve(map, name);
62. Qs! RACStream
63. Streams composable lazy/eager ops (eg throttling)
64. Streams Collections (arrays, etc) Values over time Asynchronous ops
65. Streams! no more: callbacks notifications delegates boredom
66. [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]; }];
67. __block BOOL stop = NO; __block NSError *topError = nil; CXParse *client = [CXParse clientWithApplicationId:@"my application” RESTKey:@"yeah right"]; RACSignal *login = [client login:@"johndoe" password:@"password"]; RACSignal *maps = [client GETClass:@"Map" parameters:nil]; [[[login concat:maps] takeLast:1].logAll subscribeNext:^(NSArray *maps) { NSLog(@"maps: %@", maps); } error:^(NSError *error) { topError = error; stop = YES; } completed:^{ stop = YES; }]; while (!stop && [NSRunLoop.currentRunLoop runMode:NSDefaultRunLoopMode beforeDate:NSDate.distantFuture]) ;
68. operation vs execution
69. __block BOOL stop = NO; __block NSError *topError = nil; CXParse *client = [CXParse clientWithApplicationId:@"my application" RESTKey:@"yeah right"]; RACSignal *login = [client login:@“johndoe" password:@"password"]; RACSignal *maps = [client GETClass:@“Map" parameters:nil]; [[[login concat:maps] takeLast:1].logAll subscribeNext:^(NSArray *maps) { NSLog(@"maps: %@", maps); } error:^(NSError *error) { topError = error; stop = YES; } completed:^{ stop = YES; }]; while (!stop && [NSRunLoop.currentRunLoop runMode:NSDefaultRunLoopMode beforeDate:NSDate.distantFuture]) ;
70. chaining operations
71. __block BOOL stop = NO; __block NSError *topError = nil; CXParse *client = [CXParse clientWithApplicationId:@"my application" RESTKey:@"yeah right"]; RACSignal *login = [client login:@"johndoe" password:@"password"]; RACSignal *maps = [client GETClass:@"Map" parameters:nil]; [[[login concat:maps] takeLast:1].logAll subscribeNext:^(NSArray *maps) { NSLog(@"maps: %@", maps); } error:^(NSError *error) { topError = error; stop = YES; } completed:^{ stop = YES; }]; while (!stop && [NSRunLoop.currentRunLoop runMode:NSDefaultRunLoopMode beforeDate:NSDate.distantFuture]) ;
72. testing ready
73. __block BOOL stop = NO; __block NSError *topError = nil; CXParse *client = [CXParse clientWithApplicationId:@"my application" RESTKey:@"yeah right"]; RACSignal *login = [client login:@"johndoe" password:@"password"]; RACSignal *maps = [client GETClass:@"Map" parameters:nil]; [[[login concat:maps] takeLast:1].logAll subscribeNext:^(NSArray *maps) { NSLog(@"maps: %@", maps); } error:^(NSError *error) { topError = error; stop = YES; } completed:^{ stop = YES; }]; while (!stop && [NSRunLoop.currentRunLoop runMode:NSDefaultRunLoopMode beforeDate:NSDate.distantFuture]) ;
74. gathering async ops
75. NSArray *otherUsers; return [[RACSignal concat:[otherUsers.rac_sequence map: ^RACSignal *(id user) { return [[client GETUser:user] catchTo:RACSignal.empty]; }]] collect];
76. monads!
77. [[[login flattenMap:^RACStream *(NSDictionary *login) { return [client GETRelatedTo:login className:@“_User" byKey:@"maps" parameters:nil]; }] flattenMap:^RACStream *(NSDictionary *mapsResult1) { return [client GETObjectsRelatedToCurrentUserByKey:@“maps" parameters:nil]; }] subscribeNext:^(NSDictionary *mapsResult2) { NSLog(@"maps for user: %@", @(mapsResult2.count)); } error:^(NSError *error) { topError = error; stop = YES; } completed:^{ stop = YES; }];
78. -flattenMap: = http://adit.io/posts/2013-04-17-functors,_applicatives,_and_monads_in_pictures.html
79. folds with hacks
80. RACTupleUnpack(NSArray *implicit, NSArray *explicit) = [results.rac_sequence foldLeftWithStart:RACTuplePack(NSMutableArray.array, NSMutableArray.array) reduce: ^id(RACTuple *tuple, NSDictionary *map) { NSMutableArray *receiver = [map[@"ACL"] objectForKey:acl] == nil ? tuple.first : tuple.second; [receiver addObject:map]; return tuple; }];
81. notifications
82. static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ [[NSNotificationCenter.defaultCenter rac_addObserverForName:AFNetworkingOperationDidStartNotification object:nil] subscribeNext:^(NSNotification *note) { AFHTTPRequestOperation *op = note.object; NSLog(@“%@", [TTTURLRequestFormatter cURLCommandFromURLRequest:op.request]); }]; });
83. composing nofitications
84. RACSignal *fetch = /* ... */; ! RACSignal *save = [NSNotificationCenter.defaultCenter rac_addObserverForName: NSManagedObjectContextDidSaveNotification object:CXAppDelegate.shared.managedObjectContext]; RACSignal *storeFetch = [NSNotificationCenter.defaultCenter rac_addObserverForName: AFIncrementalStoreContextDidFetchRemoteValues object:nil]; RACSignal *storeSave = [NSNotificationCenter.defaultCenter rac_addObserverForName: AFIncrementalStoreContextDidSaveRemoteValues object:nil]; RACSignal *anyUpdate = [[RACSignal merge:@[save, storeFetch, storeSave]] take:1]; ! RACSignal *rest = [anyUpdate then:^RACSignal *{ return fetch; }]; return [rest repeat];
85. composing KVO
86. self.btLogin.enabled = NO; RAC(self.btLogin.enabled) = [RACSignal combineLatest:@[ RACObserve(self, tfLogin.text), RACObserve(self, tfPassword.text) ] reduce:^(NSString *login, NSString *password) { return @(login.length > 0 && password.length > 0); }];
87. encapsulating I/O
88. - (RACSignal *)thumbnail { NSURL *url = self.thumbnailURL; if ([NSFileManager.defaultManager fileExistsAtPath:url.path] == NO) { return [[SomeViewController drawMap:self] flattenMap:^RACStream *(UIImage *m) { [UIImagePNGRepresentation(m) writeToURL:url options:NSDataWritingAtomic error:nil]; return [RACSignal return:m]; }]; } else { return [RACSignal return:[UIImage imageWithContentsOfFile:url.path]]; } }
89. op cancelation
90. [self.thumbnailCancelation sendError:[NSError errorWithDomain:NSPOSIXErrorDomain code:EINTR userInfo:nil]]; self.thumbnailCancelation = RACSubject.subject; ! [[RACSignal merge:@[[self.map thumbnail], self.thumbnailCancelation]] subscribeNext:^(UIImage *image) { self.thumbnailView.image = image; self.thumbnailView.contentMode = UIViewContentModeScaleAspectFit; self.thumbnailCancelation = nil; } error:^(NSError *error) { if (error.domain != NSPOSIXErrorDomain && error.code != EINTR) { NSLog(@"thumb error: %@ (map: %@)", error, self.map); } }];
91. tinkering
92. RACSignal *wait = [[[RACObserve(self, p12) doNext:^(id x) { NSLog(@"new p12! %@", self.p12); }] filter:^BOOL(id value) { return value != NSNull.null && value != nil; }] take:1]; ! RACSignal *access = [rq accessRequest]; access = [access doNext:^(id response) { NSLog(@"access: %@", response); }]; access = [access doError:^(NSError *error) { NSLog(@"error: %@", error); }]; ! access = [access catchTo:[RACSignal empty]]; access = [access delay:2].repeat; ! RACSignal *op = [wait then:^RACSignal *{ return access; }]; ! [op subscribeNext:^(id x) { NSLog(@"next %@", x); } error:^(NSError *error) { NSLog(@"err: %@", error); } completed:^{ NSLog(@“completed"); }];
93. return [[[self requestAuth] flattenMap:^RACStream *(NSDictionary *args) { return [[self startTunnel:args] flattenMap:^RACStream *(NMSSHSession *session) { return [[self startPortForwarding:args session:session] flattenMap:^RACStream *(NSValue *channelPointer) { LIBSSH2_CHANNEL *channel = [channelPointer pointerValue]; ! dispatch_async(self.ssh_queue, ^{ libssh2_session_set_blocking(session.session, 0); rdps_proxyloop(session.sock, channel); }); return [self rac_sessionControllerWithArgs:args]; }]; }]; }] subscribeOn:self.ssh_scheduler];
94. rac_ APIs
95. Pods/ReactiveCocoa/ReactiveCocoaFramework/ReactiveCocoa/NSData+RACSupport.h 20:+ (RACSignal *)rac_readContentsOfURL:(NSURL *)URL options:(NSDataReadingOptions)options scheduler:(RACScheduler *)scheduler; ! Pods/ReactiveCocoa/ReactiveCocoaFramework/ReactiveCocoa/NSFileHandle+RACSupport.h 17:- (RACSignal *)rac_readInBackground; ! Pods/ReactiveCocoa/ReactiveCocoaFramework/ReactiveCocoa/NSNotificationCenter+RACSupport.h 16:- (RACSignal *)rac_addObserverForName:(NSString *)notificationName object:(id)object; ! Pods/ReactiveCocoa/ReactiveCocoaFramework/ReactiveCocoa/NSString+RACSupport.h 20:+ (RACSignal *)rac_readContentsOfURL:(NSURL *)URL usedEncoding:(NSStringEncoding *)encoding scheduler:(RACScheduler *)scheduler; ! Pods/ReactiveCocoa/ReactiveCocoaFramework/ReactiveCocoa/NSURLConnection+RACSupport.h 23:+ (RACSignal *)rac_sendAsynchronousRequest:(NSURLRequest *)request; ! Pods/ReactiveCocoa/ReactiveCocoaFramework/ReactiveCocoa/NSObject+RACSelectorSignal.h 55:- (RACSignal *)rac_signalForSelector:(SEL)selector; 77:- (RACSignal *)rac_signalForSelector:(SEL)selector fromProtocol:(Protocol *)protocol; & many more
96. [[[controller rac_signalForSelector:@selector(sessionDidDisconnect:)] take:1] subscribeNext:^(id x) { [controller dismissViewControllerAnimated:NO completion:nil]; }];
97. debuggable!
98. https://github.com/ReactiveCocoa/ReactiveCocoa/tree/master/Instruments
99. beyond/without ReactiveCocoa
100. dispatch_group_create(3) libdispatch is actually pretty awesome
101. __block dispatch_group_t group = dispatch_group_create(); ! NSArray *operationsArray = /* ... */; [operationsArray enumerateObjectsUsingBlock:^(AFHTTPRequestOperation *op, NSUInteger idx, BOOL *stop) { dispatch_group_enter(group); }]; ! dispatch_group_notify(group, dispatch_get_main_queue(), ^{ [self notifyManagedObjectContext:context aboutRequestOperations:[NSArray arrayWithArray:mutableOperations] forSaveChangesRequest:saveChangesRequestCopy]; }); https://github.com/proger/AFIncrementalStore/blob/a38c0566f96525586e64639144a315f5ea0848a2/ AFIncrementalStore/AFIncrementalStore.m#L500
102. debugging dispatch (with DTrace!)
104. # mv -v /Applications/Xcode.app/Contents/Developer/Platforms/ iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator7.0.sdk/usr/lib/system/ libdispatch.dylib{,.backup} ! # cp -v /Applications/Xcode.app/Contents/Developer/Platforms/ iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator7.0.sdk/usr/lib/system/ {introspection/,}libdispatch.dylib ! # dtrace -p $(pgrep CXParseApp) -s ~/dev/darwinkit/sys/dispatch_trace.d https://github.com/proger/darwinkit/blob/master/sys/dispatch_trace.d
105. more stuff
106. -valueForKeyPath: , @keypath NSPredicate (LINQ without compile checks) create new controllers instead of reusing
107. derive state instead of keeping it
108. reason of program behaviours by isolating state impacts in your head
110. @darkproger ! http://kirillov.im kthxbai!
111. http://icomputerdenver.com/wp-content/uploads/2013/09/Mac-OS-X-Mavericks-Logo.png http://eatalkalinefoods.com/wp-content/uploads/2012/04/file0001508919007.jpg http://custom-sharepoint-training.com/wp-content/uploads/2012/02/bigstock_Crossing_Out_Reactive_And_Writ_6135701.jpg http://wallchips.com/wp-content/uploads/2013/07/Banana-Minion-mi-villano-favorito-Despicable-Me-Images.jpg http://i4.mirror.co.uk/incoming/article96108.ece/ALTERNATES/s2197/top-gun-with-tom-cruise-pic-rex-103184563-96108.jpg