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Inside Parse SDK Nikita Lutsenko @nlutsenko Facebook, Parse

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Hi » Nikita Lutsenko » @nlutsenko » Facebook » Slingshot » Parse

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Inside Parse SDK » ~730 Source Files » ~51000 Lines of Code » ~150 Classes+Protocols » 767 Unit Tests » Support for iOS, OS X » 2 Maintainers

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That's all folks. Thank you. !

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Not that simple... !

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Parse SDK » Object & File Storage » Query Engine » Local Datastore » User Authentication » Global Configuration » Analytics & Push Notifications » Much more...

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Parse SDKs now power 800 million active app-device pairs per month

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Inside Parse SDK » Promises for Asynchronous Operations » Instance/Controller/State Architecture » Lazy-loaded Dependency Injection » Written in ObjC, works in Swift » ??? » PROFIT!!!

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Promise everything! » Perform asynchronous work » Serially or in Parallel » Errors, cancellation, chaining » Unified across ObjC/Java/.NET » Light-weight and Extendable

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! Bolts.framework » Composable Promise Framework » Tasks, Executors, Cancellation Tokens » Avaialble for ObjC, Java, .NET » Open Source » github.com/BoltsFramework » Coming to Swift!

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- (NSData *)dataWithContentsOfFile:(NSString *)file { NSError *error = nil; NSData *data = [NSData dataWithContentsOfFile:file options:NSDataReadingMappedIfSafe error:&error]; return data; }

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- (NSData *)dataWithContentsOfFile:(NSString *)file error:(NSError **)error { NSData *data = [NSData dataWithContentsOfFile:file options:NSDataReadingMappedIfSafe error:&error]; return data; }

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- (void)getDataWithContentsOfFile:(NSString *)file completion:(void (^)(NSData *data))completion { dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ NSError *error = nil; NSData *data = [NSData dataWithContentsOfFile:file options:NSDataReadingMappedIfSafe error:&error]; completion(data); }); }

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- (void)getDataWithContentsOfFile:(NSString *)file completion:(void (^)(NSData *data, NSError *error))completion { dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ NSError *error = nil; NSData *data = [NSData dataWithContentsOfFile:file options:NSDataReadingMappedIfSafe error:&error]; completion(data, error); }); }

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- (void)getDataWithContentsOfFile:(NSString *)file completion:(void (^)(NSData *data, NSError *error))completion { ... } - (void)doWorkForFile:(NSString *)file { [self getDataWithContentsOfFile:file completion:^(NSData *data, NSError *error) { if (error) { [self reportError:error]; } else { [self continueWorkForData:data]; } [self deleteFile:file]; }]; }

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- (void)getDataWithContentsOfFile:(NSString *)file completion:(void (^)(NSData *data, NSError *error))completion { ... } - (void)doWorkForFile:(NSString *)file { [self getDataWithContentsOfFile:file completion:^(NSData *data, NSError *error) { if (error) { [self reportError:error]; [self deleteFile:file]; } else { [self continueWorkForData:data completion:^(NSError *error) { if (error) { [self reportError:error]; } [self deleteFile:file]; }]; } }]; }

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- (void)getDataWithContentsOfFile:(NSString *)file completion:(void (^)(NSData *data, NSError *error))completion { ... } - (void)doWorkForFile:(NSString *)file { [self getDataWithContentsOfFile:file completion:^(NSData *data, NSError *error) { if (error) { [self reportError:error]; // << Duplicate error handling ! [self deleteFile:file]; } else { [self continueWorkForData:data completion:^(NSError *error) { if (error) { [self reportError:error]; // << Duplicate error handling ! } [self deleteFile:file]; }]; } }]; }

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- (void)getDataWithContentsOfFile:(NSString *)file completion:(void (^)(NSData *data, NSError *error))completion { ... } - (void)doWorkForFile:(NSString *)file { [self getDataWithContentsOfFile:file completion:^(NSData *data, NSError *error) { if (error) { [self reportError:error]; // << Duplicate error handling ! [self deleteFile:file]; // << Duplicate code ! } else { [self continueWorkForData:data completion:^(NSError *error) { if (error) { [self reportError:error]; // << Duplicate error handling ! } [self deleteFile:file]; // << Duplicate code ! }]; } }]; }

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- (void)getDataWithContentsOfFile:(NSString *)file completion:(void (^)(NSData *data, NSError *error))completion { dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ NSError *error = nil; NSData *data = [NSData dataWithContentsOfFile:file options:NSDataReadingMappedIfSafe error:&error]; completion(data, error); }); }

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- (BFTask *)getDataAsyncWithContentsOfFile:(NSString *)file { // << Return a BFTask ! return [BFTask taskFromExecutor:[BFExecutor defaultPriorityBackgroundExecutor] withBlock:^id{ NSError *error = nil; NSData *data = [NSData dataWithContentsOfFile:file options:NSDataReadingMappedIfSafe error:&error]; if (error) { return [BFTask taskWithError:error]; } return data; }]; }

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- (BFTask *)getDataAsyncWithContentsOfFile:(NSString *)file { ... } - (void)doWorkForFile:(NSString *)file { [[[self getDataAsyncWithContentsOfFile:file] continueWithBlock:^id(BFTask *task) { if (error) { [self reportError:error]; // << Duplicate error handling ! [self deleteFile:file]; // << Duplicate code ! } else { [self continueWorkForData:data completion:^(NSError *error) { if (error) { [self reportError:error]; // << Duplicate error handling ! } [self deleteFile:file]; // << Duplicate code ! }]; } }]; }

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- (BFTask *)getDataAsyncWithContentsOfFile:(NSString *)file { ... } - (void)doWorkForFile:(NSString *)file { [[[self getDataAsyncWithContentsOfFile:file] continueWithSuccessBlock:^id(BFTask *task) { return [self continueWorkAsyncForData:data]; // << Return a BFTask ! }] continueWithBlock:^id(BFTask *task) { if (task.faulted) { [self reportError:error]; } [self deleteFile:file]; return nil; }]; }

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- (BFTask *)getDataAsyncWithContentsOfFile:(NSString *)file { ... } - (void)doWorkForFile:(NSString *)file { [[[self getDataAsyncWithContentsOfFile:file] continueWithSuccessBlock:^id(BFTask *task) { return [self continueWorkAsyncForData:data]; }] continueWithBlock:^id(BFTask *task) { if (task.faulted) { [self reportError:error]; } return [self deleteFileAsync:file]; // << Return a BFTask ! }]; }

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- (BFTask *)getDataAsyncWithContentsOfFile:(NSString *)file { ... } - (BFTask *)doWorkAsyncForFile:(NSString *)file { // << Return a BFTask ! return [[[self getDataAsyncWithContentsOfFile:file] continueWithSuccessBlock:^id(BFTask *task) { return [self continueWorkAsyncForData:data]; }] continueWithBlock:^id(BFTask *task) { if (task.faulted) { [self reportError:error]; } return [self deleteFile:file]; }]; }

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That's all good...

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But how do you manage complexity? !?

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Instance vs Controller vs State ! » Separation of Concerns and Responsbilities » Lazy Dependency Injection » No Mutable State » Thread-safe » Awesome!

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Instance vs Controller vs State » Instance ! » Public API » Immutable State » State " » Current Object State » Controller # » Acts on State » Returns State

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No content

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@interface PFFile : NSObject @property NSString *urlString; @property NSString *name; - (BFTask *)getDataInBackground; - (BFTask *)saveInBackground; @end

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@interface PFFileState : PFBaseState @property (nonatomic, copy, readonly) NSString *name; @property (nullable, nonatomic, copy, readonly) NSString *urlString; @property (nullable, nonatomic, copy, readonly) NSString *mimeType; @end @interface PFMutableFileState : PFFileState @property (nonatomic, copy, readwrite) NSString *name; @property (nullable, nonatomic, copy, readwrite) NSString *urlString; @property (nullable, nonatomic, copy, readwrite) NSString *mimeType; @end

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Base State » Base class for every state. » NSCopying, NSMutableCopying. » Equality and Comparison » -isEqual: » -compare: » -hash

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@interface PFFileState : PFBaseState @property (nonatomic, copy, readonly) NSString *name; @property (nullable, nonatomic, copy, readonly) NSString *urlString; @property (nullable, nonatomic, copy, readonly) NSString *mimeType; @end @interface PFMutableFileState : PFFileState @property (nonatomic, copy, readwrite) NSString *name; @property (nullable, nonatomic, copy, readwrite) NSString *urlString; @property (nullable, nonatomic, copy, readwrite) NSString *mimeType; @end

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@interface PFFileState : PFBaseState @property (nonatomic, copy, readonly) NSString *name; @property (nullable, nonatomic, copy, readonly) NSString *urlString; @property (nullable, nonatomic, copy, readonly) NSString *mimeType; - (instancetype)initWithState:(PFFileState *)state; + (instancetype)stateWithState:(PFFileState *)state; - (BOOL)isEqual:(id)object; - (NSInteger)hash; - (NSComparisonResult)compare:(PFFileState *)object; - (NSDictionary *)dictionaryRepresentation; - (id)debugQuickLookObject; @end

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@implementation PFFileState + (NSDictionary *)propertyAttributes { return @{ @"name" : [PFPropertyAttributes attributesWithAssociationType:PFPropertyInfoAssociationTypeCopy], @"urlString" : [PFPropertyAttributes attributesWithAssociationType:PFPropertyInfoAssociationTypeCopy], @"mimeType" : [PFPropertyAttributes attributesWithAssociationType:PFPropertyInfoAssociationTypeCopy], }; } - (id)copyWithZone:(NSZone *)zone { return [[PFFileState allocWithZone:zone] initWithState:self]; } - (instancetype)mutableCopyWithZone:(NSZone *)zone { return [[PFMutableFileState allocWithZone:zone] initWithState:self]; } @end

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@implementation PFMutableFileState @dynamic name; @dynamic urlString; @dynamic mimeType; @end

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Wait...

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How about controllers?

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@interface PFFileController : NSObject @property (nonatomic, weak, readonly) id dataSource; + (instancetype)controllerWithDataSource:(id)dataSource; - (BFTask *)downloadFileAsyncWithState:(PFFileState *)fileState... - (BFTask *)uploadFileAsyncWithState:(PFFileState *)fileState... @end

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@protocol PFCommandRunnerProvider @property (nonatomic, strong, readonly) id commandRunner; @end @protocol PFFileManagerProvider @property (nonatomic, strong, readonly) PFFileManager *fileManager; @end

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@protocol PFNoYoloControllerProvider @property (nonatomic, strong, readonly) PFNoYoloController *noYoloController; @end @protocol PFYoloControllerProvider @property (null_resettable, nonatomic, strong) PFYoloController *yoloController; @end

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- (PFYoloController *)yoloController { __block PFYoloController *controller = nil; dispatch_sync(_controllerAccessQueue, ^{ if (!_yoloController) { _yoloController = [PFYoloController controllerWithDataSource:self.dataSource]; } controller = _yoloController; }); return controller; } - (void)setYoloController:(PFYoloController *)controller { dispatch_sync(_controllerAccessQueue, ^{ _yoloController = controller; }); }

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Thank you!

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Questions? @nlutsenko github.com/BoltsFramework github.com/ParsePlatform