Data Consistency in an Unpredictable World - Swift Summit

At Pinterest, we recently completed a rewrite our iOS app (http://www.wired.com/2016/04/pinterest-reinvents-prove-really-worth-billions/). A lot of the work in an app rewrite goes unnoticed by the general public. Besides the sleek design and cool animations on the surface, one of the goals of our re-architecture was to move to a completely immutable model layer. This talk will focus on how we keep data consistent within our app with immutable models. We'll walk through updating models, loading and caching server data, and the architecture of our consistency framework.

Transcript

1. Consistency in an Unpredictable World
2. Hi, I’m Wendy! @wendyluwho
5. Emoji & Deep Learning !
9. 4 -> 3 dozen developers
10. Not all users are on the best phones, or best network Speed is important
11. "
12. Network Usage (Optimizing data sent over API) App Startup Time Concurrency
13. AVPlayer.resetAVAudioSessionCategoryToDefault() FBSDKSettings.configureForUseForApplication(application, withLaunchOptions:launchOptions) GSDAppIndexing.sharedInstance().registerApp(kAppStoreID) iRate.configureForUse() Adjust.appDidLaunch(adjustConfig) Stripe.configureForUse() DDLog.addLogger(DDTTYLogger.sharedInstance()) let fileLogger = DDFileLogger() fileLogger.logFileManager.maximumNumberOfLogFiles = 3 DDLog.addLogger(fileLogger) PIDeadlockDetector.enable() PICrash.sharedInstance().configureForUse() PINRemoteImageManager.configureForUse() CBLExperienceManager.configureForUse() NSValueTransformer.setValueTransformer(PIDateValueTransformer(), forName:kPINModelDateValueTransformerKey) CBLDeepLinkManager.sharedManager().configureServicesWithLaunchOp tions(launchOptions)
14. Moved startup tasks to low-priority concurrent queue Reduced startup time by 50%
15. AsyncDisplayKit
16. Model Layer Immutable
17. VC 1 VC 1 Pin Pin VC 2 ?!
19. Wendy Users Kanye Taylor blockUser(users[1]) #
21. A VC 2 Pin VC 1
22. Updating Models
23. Updating = Creating a new model
24. Creating from JSON Dictionary
25. let pin = Pin(dictionary:pinJSON) { "board" = { "created_at" = "Tue, 13 Aug 2013 16:38:36 +0000"; "id" = 418131215342691718; "name" = "spaces"; }; "comment_count" = 0; "description" = "At the top of my wish list for this fall is a giant chunky knit wool blanket."; "id" = "AVpd31ttshLHlWbcG9g_Kt3uVzZHjfHNvzwT20p6YnO6qzvQnqs_Z5A"; "image_square_url" = "https://s-media-cache-ak0.pinimg.com/b58cc94084407a39d62c83885ce4699e.jpg"; } Pin JSON
26. Creating from Builder Object
27. • imageURL = “https://www.123.com” Pin (Immutable) PinBuilder (Mutable) • title = “The best pin in the world” • board = “Cute Cats” • imageURL = “https://www.123.com” • title = • board = “Cute Cats” “The best pin in the world” “Meow”
28. let pin = Pin(builder:pinBuilder)
29. Loading and Caching
30. “There are only two hard things in computer science: cache invalidation, naming things, and off-by-one errors.”
31. image_url description user
32. recipe
33. PINCache
34. Cache "id": "123" Pin123 "id" = "123" "image_url" : "http://new-url.com" "recipe" : {"ingredients": ["bananas"]} "imageURL" = "http://old-url.com" "board" = "Cakery" "id" = "123" "image_url" : "http://new-url.com" “board" = "Cakery" "recipe" : {"ingredients": ["bananas"]} Pin JSON
35. Merge after initialization
36. Observing for Changes
37. Previously: KVO Notifications
39. notificationManager.addObserverForUpdatedModel(user, block:{ (NSNotification) in // Update profile view here! })
40. NSNotificationCenter.defaultCenter().addObserverForName("name", object: nil, queue: nil) { note in // ... } public func addObserverForName(name: String?, object obj: AnyObject?, queue: NSOperationQueue?, usingBlock block: (NSNotification) -> Void) -> NSObjectProtocol (__NSObserver)
41. NSNotificationCenter.defaultCenter().removeObserver(self) NSNotificationCenter.defaultCenter().removeObserver(observer)
42. notificationManager.addObserverForUpdatedModel(user, block:{ (NSNotification) in // Update profile view here! })
43. class NotificationManager: NSObject { private var observerTokens: [String: AnyObject] = [:] deinit { unregisterAll() } func unregisterAll() { for token in observerTokens.values { NSNotificationCenter.defaultCenter().removeObserver(token) } } } http://moreindirection.blogspot.com/2014/08/nsnotificationcenter-swift-and-blocks.html
44. notificationManager.addObserverForUpdatedModel(user, block:{ (NSNotification) in // Update profile view here! })
45. let newUser = PIUser(builder:builder) NotificationManager.postModelUpdatedNotificationWithObject(newUser)
46. Cache postModelUpdatedNotificationWithObject(newUser) <newUser.id> “id” = “User123” “name” = “Taylor Swift”
47. Making UI Updates
48. notificationManager.addObserverForUpdatedModel(user, block: { [weak self] notification in if let user = notification.object as? PIUser { self?.user = user // Update profile view here! self?.titleLabel.text = user.name self?.imageView.setImageWithURL(user.imageURL) } })
49. Consistency in an Unpredictable World