ITT 2014 - Peter Steinberger - Architecting Modular Codebases

Everyone knows the pain of convoluted code as an application grows and feature after feature is being added. In this talk Peter lets you explore ideas how to grow your project in a healthy, maintainable way, how to manage dependencies, how to design code around testability, how to write plugins and even some practical solutions around the idea of aspect oriented programming. This is all based on a large-scale 150k lines project and Peter shows some production code as well.

Transcript

1. Architecting Modular Codebases Istanbul Tech Talks 2014 Peter Steinberger @steipete
2. Modular what?
3. 2011 50 files 25k LOC
4. 2012 150 files 100k LOC
5. 2013 350 files 150k LOC
7. Architecting Modular Codebases » Application Components » Dependency Injection » View Controller Decoupling » Plugin Infrastructure » Aspect Oriented Programming
8. Flexibility
9. Clarity
10. Performance
11. Quality
12. What it won't do for you.
13. Application Components
14. 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
15. Application Components Structure classes after responsibility. PSPDFKit |- Gallery |- Networking |- DataExporter |-|- DataModel |- PSPDFUIKit |-|- PSPDFFoundation
16. 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
17. 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
18. Application Components Use class extensions. @interface PSPDFViewController (EmbeddedFileSupport) <PSPDFEmbeddedFilesViewControllerDelegate> @end @implementation PSPDFViewController (EmbeddedFileSupport) - (void)embeddedFilesController:(PSPDFEmbeddedFilesViewController *)controller didSelectFile:(PSPDFEmbeddedFile *)embeddedFile sender:(id)sender { // delegate implementation. }
19. Application Components Extract features into sub-controllers. * PSPDFSearchHighlightViewManager * PSPDFPresentationController * PSPDFHalfModalController objc.io/issue-1/lighter-view- controllers.html
20. Dependency Injection
21. Hollywood Principle
22. Dependency Injection - (void)viewWillDisappear:(BOOL)animated { [super viewWillDisappear:animated]; // Stop further caching the document. PSPDFCache *cache = PSPDFCache.sharedCache; [cache stopCachingDocument:self.document]; }
23. Dependency Injection - (PSPDFCache *)cache { return PSPDFCache.sharedCache; } - (void)viewWillDisappear:(BOOL)animated { [super viewWillDisappear:animated]; // Stop further caching the document. [self.cache stopCachingDocument:self.document]; }
24. Dependency Injection @property (nonatomic, strong) PSPDFCache *cache; - (void)viewWillDisappear:(BOOL)animated { [super viewWillDisappear:animated]; // Stop further caching the document. [self.cache stopCachingDocument:self.document]; }
25. Dependency Injection // In class extension @property (nonatomic, strong) PSPDFCache *cache; - (id)initWithCache:(PSPDFCache *)cache { NSParameterAssert(cache); if (self = [super init]) { _cache = cache; } return self; }
26. Dependency Injection @property (nonatomic, strong) PSPDFCache *cache; objection_requires_sel(@selector(cache)) // Create instance id vc = [JSObjection.defaultInjector getObject:ViewController.class];
27. Dependency Injection JSObjectionInjector *injector = [JSObjection createInjector]; [JSObjection setDefaultInjector:injector]; // Register singleton. [JSObjection registerClass:PSPDFCache.class scope:JSObjectionScopeSingleton];
28. Dependency Injection // Define implementation for a protocol. [self bindClass:YahooWeatherService.class toProtocol:@protocol(WeatherService)];
29. Dependency Injection Popular Frameworks » Spring, Guice » Objection » Typhoon Framework » DYI
30. View Controller Decoupling
31. View Controller Decoupling with Routes /user -> ISTUserController /user/1 -> ISTUserDetailController with ID 1
32. 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; }];
33. 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]; }
34. 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; }];
35. View Controller Decoupling with Routes » JLRoutes https://github.com/joeldev/JLRoutes » SOCKit https://github.com/NimbusKit/sockit
36. Plugin Infrastructure
37. The Apple way » CFPlugin CFPlugInAddInstanceForFactory » NSBundle builtInPlugInsPath, principalClass
38. Anatomy of a Loadable Bundle MyLoadableBundle.bundle Contents/ Info.plist MacOS/ MyLoadableBundle Resources/ Lizard.jpg MyLoadableBundle.icns en.lproj/ MyLoadableBundle.nib InfoPlist.strings
39. "iOS Static Libraries Are, Like, Really Bad, And Stuff" 15800975
40. tl;dr » Hacky "static framework" workarounds using lipo » Resource Loading » Debugging and Symbolication » Dependent frameworks » Two-level Namespacing
41. Plugin Infrastructure The Xcode way
43. 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)]; }]; }
44. Implementing Stylus Support
45. Implementing Stylus Support So many different models! » Adonit JotTouch » WACOM » Pogo (Ten One Design) » HEX3 Jaja » Unnamed Vendor
46. 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:
47. Implementing Stylus Support Places to customize: » PSPDFDrawView » PSPDFAnnotationStateManager » PSPDFFlexibleAnnotationToolbar » PSPDFViewController
48. Implementing Stylus Support New classes: » PSPDFStylusManager » PSPDFStylusViewController » PSPDFStylusStatusButton
49. Messy!
50. SDK == Driver
51. Plugin Infrastructure SDK == Driver @protocol PSPDFStylusDriver <PSPDFPlugin> - (BOOL)enableDriver:(NSError **)error options:(NSDictionary *)options; - (void)disableDriver; - (NSDictionary *)connectionInfo; @property (nonatomic, weak, readonly) id<PSPDFStylusDriverDelegate> delegate; @optional - (id<PSPDFStylusTouch>)touchInfoForTouch:(UITouch *)touch; - (UIViewController *)settingsController; @end
52. Plugin Infrastructure @protocol PSPDFPlugin <NSObject> // 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;
53. Discovery
54. 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]; }
55. Plugin Infrastructure Discovery // Static method declared in <PSPDFPlugin> + (NSDictionary *)pluginInfo { return @{PSPDFPluginNameKey : @"com.pspdfkit.stylus.driver.wacom", PSPDFPluginProtocolVersionKey : @(PSPDFPluginProtocolVersion_1), PSPDFStylusDriverNameKey : @"Wacom", PSPDFStylusDriverSDKVersionKey : WacomManager.getManager.getSDKVersion, PSPDFStylusDriverVersionKey : @(PSPDFStylusDriverProtocolVersion_1), PSPDFStylusDriverPriorityKey : @(80)}; }
56. Plugin Infrastructure Implementation @interface PSPDFAnnotationStateManagerStylusSupport : NSObject <PSPDFStylusDriverDelegate> @end @interface PSPDFAnnotationStateManager (StylusSupport) // Accessing this class will enable stylus support. - (PSPDFAnnotationStateManagerStylusSupport *)stylusSupport; @property (nonatomic, readonly) UIBarButtonItem *stylusStatusButton; @end
57. 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; }
58. 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]; } }];
59. 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
60. Plugin Infrastructure Selector Hooking Inspired by ReactiveCocoa's signals. NSObject+RACSelectorSignal.m _objc_msgForward + forwardInvocation + objc_setClass + class_replaceMethod
61. Aspect Oriented Programming
62. Aspect Oriented Programming "AOP is a programming paradigm that aims to increase modularity by allowing the separation of cross-cutting concerns."
63. Aspect Oriented Programming Advice types: » Add code before a specific method. » Add code after a specific method. » Add code instead a specific method.
64. Aspect Oriented Programming » Optional Features » Logging » Analytics » Tutorial Code
65. 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"}, ] }; }
66. 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)
67. Architecting Modular Codebases » Application Components » Dependency Injection » View Controller Decoupling » Plugin Infrastructure » Aspect Oriented Programming
68. Architecting Modular Codebases Q/A
69. 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