Building Real-Time Apps in Swift

Learn why and how to move on from simple data fetching to live queries, continuity and push notifications on iOS. In this talk we'll discuss: - Pros and Cons of moving away from RESTful data feeds and building real-time applications - Tracking changes to your data live using CloudKit - Building seamless experiences by including Handoff and Push Notifications - Sending events in real-time across multiple platforms using Swift

Transcript

1. Let’s get Real-Time! *with Swift SwiftConf, 7th September 2016, @stawecki ⚡
2. ECB Live ECB Cricket Live
3. Wonders Wonders of the Universe
4. Source: http://www.tapsmart.com/tips-and-tricks/ios-9-pull-to-refresh-your-mail-inbox-on-ipad/ “Pull to Refresh” Expectation: There may be new content User’s Responsibility: Trigger refresh. User’s Action: Scroll to where the content is expected to appear.
5. Better Expectation: Content is always up to date. It shouldn't be the user's responsibility to refresh the state of the app.
6. What is “real-time”? Source: blogs.wsj.com event / information receiver Source: no-sacred-cows.com PUSH
7. Why build real-time apps? Source: vixarix.com Relies on real-time delivery Benefits from real-time delivery
8. Why build real-time apps? Source: https://chrome.google.com/webstore/detail/google-docs/aohghmighlieiainnegkcijnfilokake http://www.iblogapple.com/2016/06/15/20-hidden-secret-features-ios-10-iphone-ipad-ipod/
9. Cost of faking real-time The ECB app checked for match data changes every 30 sec. “I can’t see the player’s stats after I see the goal happen on TV.”
10. Cost of faking real-time A note-taking app, which updates data only on “app open” or “page open” or “return to screen”. “I’ve just added a note on my Mac, why isn’t it showing up on my phone?”
11. Cost of faking real-time “If the Notes/Safari/etc. app syncs live between my devices, why doesn’t app X?”
12. On the AppStore you're competing on user experience not features.
13. Ways of doing real-time • Push Notifications and CloudKit Subscriptions: background and foreground APNs is Apple exclusive • Live TCP Connection, Live Queries: mostly foreground
14. Things I won’t go into detail • WebRTC - browser-focused set of APIs and protocols for real-time communication like: video/ audio chat, file sharing. • Messaging protocols
15. ⚡ Push Notifications
16. Push Notifications Provider or App Server Client App
17. Push Notifications api.push.apple.com Provider or App Server Client App device-token func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {…}
18. Push Notifications api.push.apple.com HTTP POST /3/device/<device-token> Provider or App Server Client App device-token Push Certificate func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [NSObject : AnyObject]) {…}
19. Push Notifications • Sample payload: (size limit - 4KB, 2KB old API) More at: https://developer.apple.com/library/mac/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/Chapters/TheNotificationPayload.html { "aps": { "alert": "New Message!", "badge": 1, "sound": "default", "content-available": 1, "category": "msg" }, "from": "Matt" }
20. Push Notifications • Receiving: func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [NSObject : AnyObject]) { if let aps = userInfo["aps"] as? NSDictionary { if let alert = aps["alert"] as? NSDictionary { if let body = alert["body"] as? NSString { print(body) } } else if let alert = aps["alert"] as? NSString { print(alert) } } }
21. Tips & Tricks!
22. Push Notifications are “cheap”: There is no charge for using APNs. • APNs Provider API is available to developers • AWS SNS: $1 per million pushes • Supports broadcast topics • SDK available in multiple languages • Don’t abuse the alerts and silent pushes, but don’t be afraid to use them! • Allow people to opt-in/out
23. Check out this one weird old trick for making millions on the AppStore! Viral App now slide to open
24. Utilise the push payload in the app: Don’t just send alerts. Propagate your UI using push data. { "aps": { "alert": "How's SwiftConf?" }, "msgs": [ { "from": "0044790123456", "ts": 1472841930959, "body": "How's SwiftConf?", "uuid": "816325" } ] }
25. Send more than “content-available”: You have 4KB of space, this should be enough for any metadata associated with the content. { "aps": { "content-available": 1 }, "notes": [ { "id": "2", "title": "Protein Waffles", "ts": "1472842680080", "rev": "3r1sQ", "thumb": “https://th.img.com/2.jpg“, } ] } Loading…
26. Send more than “content-available”: You have 4KB of space, this should be enough for any metadata associated with the content. { "aps": { "content-available": 1 }, "notes": [ { "id": "2", "title": "Protein Waffles", "ts": "1472842680080", "rev": "3r1sQ", "thumb": “https://th.img.com/2.jpg“, } ] }
27. https://developer.apple.com/library/mac/documentation/NetworkingInternet/ Conceptual/RemoteNotificationsPG/Chapters/TheNotificationPayload.html “Delivery of notifications is a “best effort”, not guaranteed. It is not intended to deliver data to your app, only to notify the user that there is new data available.”
28. Push & Pull: Pre-fill with push data, pull data feed to validate. { "aps": { … }, "notes": [ { "id": "2", "title": "Protein Waffles", "ts": "1472842680080", "rev": "3r1sQ" } ] } 1. Push Received 2. Show placeholders 3. Load Feed [ { "id": "2", "title": "Protein Waffles", "text": "…", "ts": "1472842680080", "rev": "3r1sQ" }, { "id": "1", "title": "Vegan Cake", "text": "…", "ts": "1461231040080", "rev": “z8iF0" } ] 4. Update UI with Feed
29. Push & Pull • When Push fails, use standard app events. • Trigger with Handoff (NSUserActivity) • If Push Notifications are required anyway, why add sockets on top?
30. Sync Issues (merging two data sources): • Use IDs and Time-stamps • Keep deleted records, but mark as deleted. • See: “Vesper Sync Diary” by Brent Simmons Push & Pull
31. Consider sending partial data: With 4KB you can experiment with sending POIs, partial text content, prefetched URLs, ratings, even thumbnails. 2422 bytes Base64 1814 bytes binary
32. Checkout changes to Notifications in iOS10 • UserNotifications.framework & UNNotification class • Notification Service Extension - handle payload
 before notification is shown, download media. • Notification Content Extension
 - custom notification UI Source:
 Advanced Notifications - WWDC 2016 - Session 708
33. Use SNS topics to mix between APNs, SQS and more: Simplify your backend code by making it transport-agnostic. Message SNS Topic APNs SQS Queue HTTP Endpoint WebSocket Service E-mail Service iOS Device
34. • Code sample - Registering Device Token with AWS: func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) { let deviceTokenString: String = (deviceToken.description as String) .trimmingCharacters(in: CharacterSet(charactersIn: "<>")) .replacingOccurrences(of: " ", with: "") as String let sns = AWSSNS.default() let request = AWSSNSCreatePlatformEndpointInput() request?.token = deviceTokenString request?.platformApplicationArn = "app:arn:.." sns.createPlatformEndpoint(request!) .continue(with: AWSExecutor.mainThread(), with: { (task: AWSTask!) -> AnyObject! in if task.error != nil { print("Error: \(task.error)") } else { let createEndpointResponse = task.result! as AWSSNSCreateEndpointResponse print("endpointArn: \(createEndpointResponse.endpointArn)") } return nil }) }
35. • Code sample - Broadcast to topic with AWS SNS: let sns = AWSSNS.default() let request = AWSSNSPublishInput() request?.message = "Hello Users!" request?.topicArn = "arn:aws:sns:us-west-2:0123456:all-users" sns.publish(request!) .continue(with: AWSExecutor.mainThread(), with: { (task: AWSTask!) -> AnyObject! in if task.error != nil { print("Error: \(task.error)") } return nil })
36. ☁ CloudKit
37. CloudKit • iOS framework for accessing an iCloud-managed database system. • Supports: client, server to server, browser. • Simple real-time capabilities with Subscriptions
38. CloudKit • Sample usage - Adding a Record: let db = CKContainer.default().publicCloudDatabase let matchID = CKRecordID(recordName: "1") let place = CKRecord(recordType: "Match", recordID: matchID) place.setObject("John Smith vs Amy Bloggs", forKey: "title") place.setObject("YES", forKey: "live") place.setObject("0:0", forKey: "score") db.save(place) { savedRecord, error in // handle errors: print(error.debugDescription) }
39. CloudKit • Sample usage - Fetching a Record: let db = CKContainer.default().publicCloudDatabase let matchID = CKRecordID(recordName: "1") db.fetch(withRecordID: matchID) { match, error in print(match.debugDescription) self.showScore(title: match?.value(forKey: "title") as! String, score: match?.value(forKey: "score") as! String) }
40. CloudKit • Creating a Subscription: let db = CKContainer.default().publicCloudDatabase let predicate = NSPredicate(format:"live = %@", "YES") let subscription = CKQuerySubscription(recordType: "Match", predicate: predicate, options: .firesOnRecordUpdate) let notification = CKNotificationInfo() notification.alertLocalizationKey = "MATCH_UPDATE" notification.alertLocalizationArgs = ["title", "score"] notification.desiredKeys = ["title", "score"] notification.soundName = "default" subscription.notificationInfo = notification db.save(subscription, completionHandler: { (result, error) -> Void in if error != nil { print(error!.localizedDescription) } })
41. CloudKit • Receiving Subscription notification: func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [NSObject : AnyObject]) { let notification = CKNotification(fromRemoteNotificationDictionary: userInfo as! [String : NSObject]) if notification.notificationType == .query, let result = notification as? CKQueryNotification { // Fill in data from notification: (PUSH) vc.showScore(title: (result.recordFields?["title"] as! String)+"*", score: result.recordFields?["score"] as! String) // Fetch full record based on ID: (& PULL) let recordID = result.recordID vc.loadScore(recordId: recordID!) } }
43. CloudKit Subscriptions: • Registered per user’s iCloud account
 (unlike a “live query” which is usually active during runtime) • No need to manage push credentials or tokens • App logic can focus on Record operations • Support “content-available” and categories
44. • CloudKit Best Practices
 WWDC 2016 - Session 231 • Introduction to Notifications
 WWDC 2016 - Session 707 • Advanced Notifications
 WWDC 2016 - Session 708 • What's New in the Apple Push Notification Service
 WWDC 2016 - Session 724
45. Cross-platform
46. Challenges in Swift Cross-platform changes everything! • For non-iOS, leverage services:
 Google PubSub, AWS SQS+SNS, PubNub, Firebase, Pusher • Server-side Swift’s HTTP libraries open up a world of services regardless of SDK support.
47. Live Queries let messagesQuery = Message.query()? .whereKey("roomName", equalTo: "general") ParseLiveQuery.Client() .subscribe( messagesQuery ) .handle(Event.Created) { _, message in self.printMessage(message) } https://github.com/ParsePlatform/ParseLiveQuery-iOS-OSX
48. Challenges in Swift Cross-platform code reuse: • decouple your code • use dependency injection • make sure your models are serialisable • prove your concept works on the server first Source: http://www.johndcook.com/blog/2011/07/19/you-wanted-banana/
49. Architecture Challenges DynamoDB ContentRenderer func renderHTML(node:ContentNode, session:AppSession) -> String { } WebAppSession : AppSession LocalAppSession : AppSession var sessionCookie = String() RxSwift SNS FileManager Server iOS func userSettings() func userSettings()
50. Push at Tapjet
52. Push @ Tapjet Dropbox File Change Fetch Delta Sync Task List folder, enqueue import tasks, write to node graph Enque Sync Tasks Generate new Snapshot Write to asset graph Update Preview App Download processed files
53. Push @ Tapjet Dropbox File Change Fetch Delta Sync Task List folder, enqueue import tasks, write to node graph Enque Sync Tasks Generate new Snapshot Write to asset graph Update Preview App Download processed files web-hook MQ long polling Subscription: task status Silent push: snapshot ID and metadata Subscription: asset status backend device
54. Push @ Tapjet Latency Interval
 (worst case) Web-hook 250ms 5s MQ polling 80ms 5s Subscription (server) 150ms 5s Silent push 500ms 5s Subscription (remote) 350ms 5s Total: 1.3s 25s Comparing push with time-based checks
55. User Experience transcends implementation method. Doesn’t matter how you do it. It matters whether it works well.
56. Enjoy the rest of SwiftConf! My notifications are ON. @stawecki