Objective-C on Lambdas - Speaker Deck

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ƛavericks @darkproger

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Functional Programming with Objective-C

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Objective-C (the good parts) Static typing Dynamic binding Blocks ARC

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Objective-C (really) Boring Verbose Low-level OOP

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-[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

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[headerView addConstraint:[NSLayoutConstraint constraintWithItem:excessivelyBigView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationLessThanOrEqual toItem:headerView attribute:NSLayoutAttributeHeight multiplier:0.0 constant:45]]; AutoLayout

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- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { if ([keyPath isEqualToString:@"state"]) { /* ... */ } } KVO

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NSMutableArray *result = [NSMutableArray arrayWithCapacity:mutableOperations.count]; [mutableOperations enumerateObjectsUsingBlock:^(AFHTTPRequestOperation *op, NSUInteger idx, BOOL *stop) { [result addObject:change_op(op)]; }]; return result;

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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) { +

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…state?

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you ok? you good? you need anything? you sure you’re fine? argh!!

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you ok? you good? you need anything? you sure you’re fine? argh!!

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you ok? you good? you need anything? you sure you’re fine? argh!! STATE SUCKS!

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singletons too (dispatch_once story here)

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Functional no state!

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Functional HOFs

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Functional HOFs HOFs > OOP patterns

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Functional immutable data no side effects .. thread-safe

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Functional simple

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> 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)]

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Functional declarative rather than imperative

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NSMutableArray

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NSArray

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NSArray *newMaps = [maps map:^id(CXMap *map) { return [map changeSomehow]; }]; http://underscorem.org/ https://github.com/mogeneration/functionalkit and more!

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NSArray *newMaps = [maps map:^id(CXMap *map) { return [map changeSomehow]; }]; entirely new array! mapping function (HOF) returns a new object

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Function Composition

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> 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

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> 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

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> 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 ^

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> let f = foldl1 (+) . filter even . map (+1) > :type f f :: [Integer] -> Integer > f numbers 12 int f(int array[])

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> let f = foldl1 (+) . filter even . map (+1) > :type f f :: [Integer] -> Integer > f numbers 12 int f(int array[]) NSInvocation a block

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Functors http://adit.io/posts/2013-04-17-functors,_applicatives,_and_monads_in_pictures.html

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> let numbers = [1,2,3,4,5] > fmap (+1) numbers [2,3,4,5,6] ! > fmap (+1) (Just 2) Just 3

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Concurrency

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[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]; }];

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-> * login * load data from cache * load data from network * send stats

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report_stats( load_network( load_cached( login(user)))

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dashboard = login . load_cache . load_network . report_stats

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scripts != apps

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Objective-C concurrency -scheduleInRunLoop:

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Objective-C concurrency NSThread @synchronized

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Objective-C advanced concurrency dispatch(3)

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Qs! units of work NSRunLoop dispatch_queue NSOperationQueue

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Qs! actors (queues associated with an execution context) ! -performSelector: https://code.google.com/p/plankton-platform/ https://code.google.com/p/plactorkit/

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true for motivational training losers different story in (user-oriented) programming

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ReactiveCocoa

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pod 'ReactiveCocoa', '~> 2.1.3'

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- self.title = [map name]; + RAC(self, title) = RACObserve(map, name);

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Qs! RACStream

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Streams composable lazy/eager ops (eg throttling)

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Streams Collections (arrays, etc) Values over time Asynchronous ops

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Streams! no more: callbacks notifications delegates boredom

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__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]) ;

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operation vs execution

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__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]) ;

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chaining operations

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__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]) ;

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testing ready

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__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]) ;

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gathering async ops

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NSArray *otherUsers; return [[RACSignal concat:[otherUsers.rac_sequence map: ^RACSignal *(id user) { return [[client GETUser:user] catchTo:RACSignal.empty]; }]] collect];

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monads!

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[[[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; }];

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-flattenMap: = http://adit.io/posts/2013-04-17-functors,_applicatives,_and_monads_in_pictures.html

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folds with hacks

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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; }];

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notifications

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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]); }]; });

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composing nofitications

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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];

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composing KVO

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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); }];

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encapsulating I/O

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- (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]]; } }

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op cancelation

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[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); } }];

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tinkering

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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"); }];

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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];

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rac_ APIs

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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

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[[[controller rac_signalForSelector:@selector(sessionDidDisconnect:)] take:1] subscribeNext:^(id x) { [controller dismissViewControllerAnimated:NO completion:nil]; }];

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debuggable!

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https://github.com/ReactiveCocoa/ReactiveCocoa/tree/master/Instruments

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beyond/without ReactiveCocoa

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dispatch_group_create(3) libdispatch is actually pretty awesome

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__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

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debugging dispatch (with DTrace!)

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# 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

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more stuff

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-valueForKeyPath: , @keypath NSPredicate (LINQ without compile checks) create new controllers instead of reusing

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derive state instead of keeping it

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reason of program behaviours by isolating state impacts in your head

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@darkproger ! http://kirillov.im kthxbai!

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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