iAsync Functional Programming in Objective-C

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iAsync Functional Programming in Objective-C Alexander Dodatko 2013

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Over 900,000 apps (as of June 2013)

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NSData* jsonData = nil; jsonData = [ NSData dataWithContentsOfURL: RESOURSE ];

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Asynchronous Programming

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@protocol NSURLConnectionDataDelegate @optional - (void)connection: didReceiveResponse: - (void)connection: didReceiveData: - (void)connectionDidFinishLoading: - (void)connection: didFailWithError: @end

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Too Much Code

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Objectice-C Blocks

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NS_AVAILABLE(10_7, 5_0); + (void)sendAsynchronousRequest: queue: completionHandler:

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void (^HANDLER_BLOCK)( NSURLResponse* response, NSData* data, NSError* connectionError)

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Progress Cancel

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NSURL *url = [NSURL URLWithString:@"https://...."]; NSURLRequest *request = [NSURLRequest requestWithURL:url]; id onSuccess = ^(NSURLRequest *, NSHTTPURLResponse *, id JSON) { NSLog( @"App.net Global Stream: %@", JSON ); }; AFJSONRequestOperation *operation = [ AFJSONRequestOperation JSONRequestOperationWithRequest: request success: onSuccess failure: nil ]; [ operation start ];

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Dependencies

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When using methods which return blocks they can be very convenient. However, when you have to string a few of them together it gets messy really quickly

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[remoteAPIWithURL:url1 success:^(int status){ [remoteAPIWithURL:url2 success:^(int status){ [remoteAPIWithURL:url3 success:^(int status){ [remoteAPIWithURL:url2 success:^(int status){ //success!!! }]; }]; }]; }];

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It was not uncommon when using AFNetworking in Gowalla to have calls chained together in success blocks. My advice would be to factor the network requests and serializations as best you can into class methods in your model. Then, for requests that need to make sub-requets, you can call those methods in the success block.

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Callback Hell

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AFURLConnectionOperation

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Working with independent data sets in parallel and then combining them into a final result is non-trivial in Cocoa, and often involves a lot of synchronization

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__block NSArray *databaseObjects, fileContents; NSOperationQueue *backgroundQueue = [[NSOperationQueue alloc] init]; NSBlockOperation *databaseOperation = [NSBlockOperation blockOperationWithBlock:^{ databaseObjects = [databaseClient fetchObjectsMatchingPredicate:predicate]; }]; NSBlockOperation *filesOperation = [NSBlockOperation blockOperationWithBlock:^{ NSMutableArray *filesInProgress = [NSMutableArray array]; for (NSString *path in files) { [filesInProgress addObject:[NSData dataWithContentsOfFile:path]]; } fileContents = [filesInProgress copy]; }]; NSBlockOperation *finishOperation = [NSBlockOperation blockOperationWithBlock:^{ [self finishProcessingDatabaseObjects:databaseObjects fileContents:fileContents]; NSLog(@"Done processing"); }]; [finishOperation addDependency:databaseOperation]; [finishOperation addDependency:filesOperation]; [backgroundQueue addOperation:databaseOperation]; [backgroundQueue addOperation:filesOperation]; [backgroundQueue addOperation:finishOperation];

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Rather than using mutable variables which are replaced and modified in-place, RAC provides signals (represented by RACSignal) that capture present and future values.

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When Design Patterns are NOT enough

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Meet the Async Operation CancelBlock (^AsyncOperation) ( ProgressCallback, CancelCallback, CompletionCallback ) {...};

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Sequence JFFAsyncOperation sequence = sequenceOfAsyncOperations( @[ op1, op2, opN ] );

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Sequence of Attempts JFFAsyncOperation sequence = trySequenceOfAsyncOperations( @[ op1, op2, opN ] );

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Parallel execution JFFAsyncOperation sequence = groupOfAsyncOperations( @[ op1, op2, opN ] ); CompletionCallback

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Waterfall JFFAsyncOperation sequence = bindSequenceOfAsyncOperations( op1, @[ b1, b2, bN ] );

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Function = Command + Composite

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Any Complexity Tasks

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loadFromNet = sequenceOfAsyncOperations( @[ login, loadFromNet ] ); loadRawData = trySequenceOfAsyncOperations( @[ loadFromFSCache, loadFromNet ] ); JFFAsyncOperation getData = bindSequenceOfAsyncOperations( loadRawData, @[ parseBinder, filterBinder ] );

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iAsync bit.ly/1bLdN59

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Does anyone use it?

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Wishdates

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Sitecore

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Pitfalls Large codebase No PodSpec No Documentation No Community No Versioning policy

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Vladimir Gorbenko [email protected] Vova.Gorbenko.mac github.com/volodg iAsync Author

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Oleksandr Dodatko [email protected] alexander.dodatko.work @dodikk88 github.com/dodikk

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