Architecting Modular Codebases

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Architecting Modular Codebases Istanbul Tech Talks 2014 Peter Steinberger @steipete

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Modular what?

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2011 50 ﬁles 25k LOC

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2012 150 ﬁles 100k LOC

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2013 350 ﬁles 150k LOC

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2014

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Architecting Modular Codebases » Application Components » Dependency Injection » View Controller Decoupling » Plugin Infrastructure » Aspect Oriented Programming

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Flexibility

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Clarity

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Performance

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Quality

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What it won't do for you.

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Application Components

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Find large ﬁles ﬁnd . -name "*.m" -exec wc -l "{}" \; | sort -rn | head 4351 ./TextParser/PSPDFFontFileDescriptor.m 3651 ./Controller/PSPDFViewController.m 2889 ./Views/PSPDFPageView.m 2189 ./Parser/PSPDFDocumentParser.m 2017 ./XFDF/PSPDFXFDFParser.m 2004 ./Model/PSPDFDocument.m 1783 ./TextParser/PSPDFTextParser.m 1776 ./Annotations/PSPDFAnnotation.m 1649 ./Views/PSPDFPageView+AnnotationMenu.m 1469 ./Gallery/PSPDFGalleryViewController.m

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Application Components Use private headers within components. PSPDFEmbeddedFile.h/m PSPDFEmbeddedFile+Private.h @interface PSPDFEmbeddedFile (Private) // Parses the PDF dictionary and returns an `PSPDFEmbeddedFile` object if found. + (instancetype)embeddedFileWithPDFDictionary:(CGPDFDictionaryRef)pdfDictionary; // Index of the ﬁle in the original document. @property (nonatomic, copy) NSString *streamPath; @end

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Application Components Use class extensions. @interface UIView (UIViewHierarchy) - (void)layoutSubviews; @end @interface UIView (UIViewRendering) - (void)drawRect:(CGRect)rect; @end @interface UIView (UIViewGestureRecognizers) - (void)addGestureRecognizer:(UIGestureRecognizer*)recognizer @end @interface UIView (UIViewMotionEffects) - (void)addMotionEffect:(UIMotionEffect *)effect @end

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Application Components Use class extensions. @interface PSPDFViewController (EmbeddedFileSupport) @end @implementation PSPDFViewController (EmbeddedFileSupport) - (void)embeddedFilesController:(PSPDFEmbeddedFilesViewController *)controller didSelectFile:(PSPDFEmbeddedFile *)embeddedFile sender:(id)sender { // delegate implementation. }

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Application Components Extract features into sub-controllers. * PSPDFSearchHighlightViewManager * PSPDFPresentationController * PSPDFHalfModalController objc.io/issue-1/lighter-view- controllers.html

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Dependency Injection

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Hollywood Principle

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Dependency Injection - (void)viewWillDisappear:(BOOL)animated { [super viewWillDisappear:animated]; // Stop further caching the document. PSPDFCache *cache = PSPDFCache.sharedCache; [cache stopCachingDocument:self.document]; }

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Dependency Injection - (PSPDFCache *)cache { return PSPDFCache.sharedCache; } - (void)viewWillDisappear:(BOOL)animated { [super viewWillDisappear:animated]; // Stop further caching the document. [self.cache stopCachingDocument:self.document]; }

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Dependency Injection @property (nonatomic, strong) PSPDFCache *cache; - (void)viewWillDisappear:(BOOL)animated { [super viewWillDisappear:animated]; // Stop further caching the document. [self.cache stopCachingDocument:self.document]; }

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Dependency Injection // In class extension @property (nonatomic, strong) PSPDFCache *cache; - (id)initWithCache:(PSPDFCache *)cache { NSParameterAssert(cache); if (self = [super init]) { _cache = cache; } return self; }

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Dependency Injection @property (nonatomic, strong) PSPDFCache *cache; objection_requires_sel(@selector(cache)) // Create instance id vc = [JSObjection.defaultInjector getObject:ViewController.class];

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Dependency Injection JSObjectionInjector *injector = [JSObjection createInjector]; [JSObjection setDefaultInjector:injector]; // Register singleton. [JSObjection registerClass:PSPDFCache.class scope:JSObjectionScopeSingleton];

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Dependency Injection // Deﬁne implementation for a protocol. [self bindClass:YahooWeatherService.class toProtocol:@protocol(WeatherService)];

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Dependency Injection Popular Frameworks » Spring, Guice » Objection » Typhoon Framework » DYI

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View Controller Decoupling

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View Controller Decoupling with Routes /user -> ISTUserController /user/1 -> ISTUserDetailController with ID 1

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View Controller Decoupling with Routes // Set up routes [JLRoutes addRoute:@"/user/:userID" handler:^BOOL(NSDictionary *parameters) { NSUInteger userID = [parameters[@"userID"] integerValue]; UserDetailController *controller = [[UserDetailController alloc] initWithID:userID]; [self.navigationController pushViewController:controller animated:YES]; return YES; }];

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View Controller Decoupling with Routes // Open the user controller. NSUInteger userID = 42; NSString *URLString = [NSString stringWithFormat:@"myapp://user/%tu?animated=NO", userID]; [UIApplication.sharedApplication openURL:[NSURL URLWithString:URLString]]; // Install the URL handler. - (BOOL)application:(UIApplication *)app openURL:(NSURL *)URL sourceApplication:(NSString *)source annotation:(id)annotation { return [JLRoutes routeURL:URL]; }

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View Controller Decoupling with Routes // Set up route and also process the animation property. [JLRoutes addRoute:@"/user/:userID" handler:^BOOL(NSDictionary *parameters) { NSUInteger userID = [parameters[@"userID"] integerValue]; BOOL animated = parameters[@"animated"] ? [parameters[@"animated"] boolValue] : YES; UserDetailController *controller = [[UserDetailController alloc] initWithID:userID]; [self.navigationController pushViewController:controller animated:animated]; return YES; }];

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View Controller Decoupling with Routes » JLRoutes https://github.com/joeldev/JLRoutes » SOCKit https://github.com/NimbusKit/sockit

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Plugin Infrastructure

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The Apple way » CFPlugin CFPlugInAddInstanceForFactory » NSBundle builtInPlugInsPath, principalClass

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Anatomy of a Loadable Bundle MyLoadableBundle.bundle Contents/ Info.plist MacOS/ MyLoadableBundle Resources/ Lizard.jpg MyLoadableBundle.icns en.lproj/ MyLoadableBundle.nib InfoPlist.strings

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"iOS Static Libraries Are, Like, Really Bad, And Stuff" 15800975

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tl;dr » Hacky "static framework" workarounds using lipo » Resource Loading » Debugging and Symbolication » Dependent frameworks » Two-level Namespacing

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Plugin Infrastructure The Xcode way

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Plugin Infrastructure The Xcode way + (void)pluginDidLoad:(NSBundle *)plugin { // Initialize class } // BBUDebuggerTuckAway - (void)swizzleDidChangeTextInSourceTextView { id sourceTextView = [objc_getClass("DVTSourceTextView") new]; [sourceTextView yl_swizzleSelector:@selector(didChangeText) withBlock:^void(id _self) { [self toggleDebuggersIfNeeded]; // call original [_self yl_performSelector:@selector(didChangeText)]; }]; }

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Implementing Stylus Support

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Implementing Stylus Support So many different models! » Adonit JotTouch » WACOM » Pogo (Ten One Design) » HEX3 Jaja » Unnamed Vendor

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Implementing Stylus Support Different approaches! » UIApplication subclass/hook sendEvent: » Register/deregister views » Custom touch delivery » Touch classiﬁcation » Manually forwarding touches from touchesBegan:/Moved:/Ended:/Cancelled:

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Implementing Stylus Support Places to customize: » PSPDFDrawView » PSPDFAnnotationStateManager » PSPDFFlexibleAnnotationToolbar » PSPDFViewController

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Implementing Stylus Support New classes: » PSPDFStylusManager » PSPDFStylusViewController » PSPDFStylusStatusButton

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Messy!

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SDK == Driver

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Plugin Infrastructure SDK == Driver @protocol PSPDFStylusDriver - (BOOL)enableDriver:(NSError **)error options:(NSDictionary *)options; - (void)disableDriver; - (NSDictionary *)connectionInfo; @property (nonatomic, weak, readonly) id delegate; @optional - (id)touchInfoForTouch:(UITouch *)touch; - (UIViewController *)settingsController; @end

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Plugin Infrastructure @protocol PSPDFPlugin // Designated initializer. Will be called upon creation. - (id)initWithRegistry:(PSPDFPluginRegistry *)registry options:(NSDictionary *)options; // Plugin details for auto-discovery. + (NSDictionary *)pluginInfo; @end extern NSString * const PSPDFPluginNameKey; extern NSString * const PSPDFPluginEnabledKey; extern NSString * const PSPDFPluginInitializeOnDiscoveryKey; extern NSString * const PSPDFPluginSaveInstanceKey; extern NSString * const PSPDFPluginProtocolVersionKey;

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Discovery

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Plugin Infrastructure Discovery - (NSDictionary *)discoverPluginClasses { NSMutableDictionary *pluginClasses = [NSMutableDictionary dictionary]; // Interate all classes. unsigned int count = 0; Class *classList = objc_copyClassList(&count); for (int index = 0; index < count; index++) { Class class = classList[index]; if (class_conformsToProtocol(class, @protocol(PSPDFPlugin)) && [self isValidPluginClass:class]) { NSDictionary *info = [class pluginInfo]; pluginClasses[info[PSPDFPluginNameKey]] = class; } } free(classList); return [pluginClasses copy]; }

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Plugin Infrastructure Discovery // Static method declared in + (NSDictionary *)pluginInfo { return @{PSPDFPluginNameKey : @"com.pspdfkit.stylus.driver.wacom", PSPDFPluginProtocolVersionKey : @(PSPDFPluginProtocolVersion_1), PSPDFStylusDriverNameKey : @"Wacom", PSPDFStylusDriverSDKVersionKey : WacomManager.getManager.getSDKVersion, PSPDFStylusDriverVersionKey : @(PSPDFStylusDriverProtocolVersion_1), PSPDFStylusDriverPriorityKey : @(80)}; }

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Plugin Infrastructure Implementation @interface PSPDFAnnotationStateManagerStylusSupport : NSObject @end @interface PSPDFAnnotationStateManager (StylusSupport) // Accessing this class will enable stylus support. - (PSPDFAnnotationStateManagerStylusSupport *)stylusSupport; @property (nonatomic, readonly) UIBarButtonItem *stylusStatusButton; @end

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Plugin Infrastructure Implementation // Lazily initialize our stylus support class. - (PSPDFAnnotationStateManagerStylusSupport *)stylusSupport { PSPDFAnnotationStateManagerStylusSupport *stylusSupport = objc_getAssociatedObject(self, _cmd); if (!stylusSupport) { stylusSupport = [[PSPDFAnnotationStateManagerStylusSupport alloc] initWithStateManager:self]; objc_setAssociatedObject(self, _cmd, stylusSupport, OBJC_ASSOCIATION_RETAIN); } return stylusSupport; }

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Plugin Infrastructure Implementation // Hook into didMoveToWindow for view registration. [PSPDFDrawView.class pspdf_hookSelector:@selector(didMoveToWindow) withBlock:^(PSPDFDrawView *view, NSArray *args) { if (view.window) { [PSPDFStylusManager.sharedInstance registerView:view]; }else { [PSPDFStylusManager.sharedInstance unregisterView:view]; } }];

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Plugin Infrastructure Implementation @interface NSObject (PSPDFMessageHooks) - (BOOL)pspdf_hookSelector:(SEL)selector withBlock:(void (^)(id object, NSArray *arguments))block; + (BOOL)pspdf_hookSelector:(SEL)selector withBlock:(void (^)(id object, NSArray *arguments))block; @end

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Plugin Infrastructure Selector Hooking Inspired by ReactiveCocoa's signals. NSObject+RACSelectorSignal.m _objc_msgForward + forwardInvocation + objc_setClass + class_replaceMethod

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Aspect Oriented Programming

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Aspect Oriented Programming "AOP is a programming paradigm that aims to increase modularity by allowing the separation of cross-cutting concerns."

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Aspect Oriented Programming Advice types: » Add code before a specific method. » Add code after a specific method. » Add code instead a specific method.

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Aspect Oriented Programming » Optional Features » Logging » Analytics » Tutorial Code

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Aspect Oriented Programming - (NSDictionary *)analyticsConﬁguration { return @{ @"trackedScreens" : @[ @{@"class" : @"ISTMainViewController", @"label" : @"Main screen"} ], @"trackedEvents" : @[ @{@"class" : @"ISTMainViewController", @"sel" : @"loginWithFacebook:", @"label" : @"Login with Facebook"}, @{@"class" : @"ISTFacebookViewController", @"sel" : @"failedToConnect:", @"label" : @"Facebook connection failure"}, ] }; }

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Aspect Oriented Programming » AOP-for-Objective-C https://github.com/ndcube/AOP-for- Objective-C » NSProxy » ReactiveCocoa https://github.com/ReactiveCocoa/ ReactiveCocoa » method_exchangeImplementations (DIY)

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Architecting Modular Codebases » Application Components » Dependency Injection » View Controller Decoupling » Plugin Infrastructure » Aspect Oriented Programming

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Architecting Modular Codebases Q/A

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Architecting Modular Codebases Thanks! Resources: * http://www.typhoonframework.org * https://github.com/atomicobject/objection * http://objc.io/issue-1/lighter-view-controllers.html * https://github.com/joeldev/JLRoutes * http://ddeville.me/2014/04/dynamic-linking/ * http://dev.hubspot.com/blog/architecting-a-large-ios-app-with-cocoapods * http://landonf.bikemonkey.org/code/ios/Radar_15800975_iOS_Frameworks.20140112.html * https://github.com/neonichu/BBUDebuggerTuckAway * http://albertodebortoli.github.io/blog/2014/03/25/ an-aspect-oriented-approach-programming-to-ios-analytics/ * http://codeshaker.blogspot.co.at/2012/01/aop-delivered.html * https://github.com/ReactiveCocoa/ReactiveCocoa/blob/master/ ReactiveCocoaFramework/ReactiveCocoa/NSObject+RACSelectorSignal.m * https://github.com/ndcube/AOP-for-Objective-C * http://codeshaker.blogspot.com.tr/2012/01/aop-delivered.html Image Credits: * Hollywood, Gavin Johnson, ﬂickr.com/photos/23629211@N04/4569636150