Reactive Programming with Realm

This talk gives an introduction into the basic concepts of Realm and some insights how it works under the hood. Building on these basics, it ended up in exploring together with the audience in a live coding session, how just Realm alone can be central to the architecture of reactive applications.

Transcript

1. ⚗ Reactive Programming with Realm
3. What is Realm & How does it work?
4. What is Realm not?
5. Realm is not an ORM. Realm is the database itself.
6. Embedded NoSQL Object-oriented Database
7. Embedded = Built from scratch for !
8. ⚡ SQLite
9. NoSQL = Schema-free? No, too slow. !
10. Object-oriented
11. class Person : Object { dynamic var name = "" dynamic var age = 0 let children = List<Person>() let parents = LinkingObjects(fromType: Person.self, property: "children") }
12. You directly interact with memory-mapped data.
13. All retrieved objects are just pointers to their data. @interface RLMObjectBase () { realm::Row _row; } @end namespace realm { class Row { TableRef m_table; size_t m_row_ndx; } }
14. Their classes describe how to read from there and navigate within the file.
15. But let's take a closer look how the data structure looks like.
16. Realm !"" Versions !"" Tables !"" Columns !"" Values
17. The root level describes the different versions ! " #
18. ACID • Atomicity • Consistency • Isolation • Durability
19. Naïve
20. Multi Version Concurrency Control
24. Copy-on-Write
26. Live Objects class Message : Object { dynamic var text = "" } let realm = try! Realm() let feed = realm.objects(Message) feed.count // => 0 let hello = Message() hello.text = "Hello!" try! realm.write { realm.add(hello) } feed.count // => 1 !
27. Built-in Notifications • File-wide Observation • Fine-grained Notifications on Collections • Key-Value-Observing compliant
28. File-wide Observation // Observe Realm Notifications let token = realm.addNotificationBlock { notification, realm in viewController.updateUI() } // later token.stop()
29. Fine-grained Notifications let results = realm.objects(Person).filter("age > 5") // Observe Results Notifications notificationToken = results.addNotificationBlock { [weak self] (changes: RealmCollectionChange) in guard let tableView = self?.tableView else { return } switch changes { case .Initial: // Results are now populated and can be accessed without blocking the UI tableView.reloadData() break case .Update(_, let deletions, let insertions, let modifications): // Query results have changed, so apply them to the UITableView tableView.beginUpdates() tableView.insertRowsAtIndexPaths(insertions.map { NSIndexPath(forRow: $0, inSection: 0) }, withRowAnimation: .Automatic) tableView.deleteRowsAtIndexPaths(deletions.map { NSIndexPath(forRow: $0, inSection: 0) }, withRowAnimation: .Automatic) tableView.reloadRowsAtIndexPaths(modifications.map { NSIndexPath(forRow: $0, inSection: 0) }, withRowAnimation: .Automatic) tableView.endUpdates() break case .Error(let error): // An error occurred while opening the Realm file on the background worker thread fatalError("\(error)") break } }
30. Key-Value-Observing func addObservers() { self.addObserver(self, forKeyPath: "entry.title", options: [], context: nil) self.addObserver(self, forKeyPath: "entry.date", options: [], context: nil) } override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) { if keyPath == "entry.title" { self.textLabel!.text = entry.title } else if keyPath == "entry.date" { self.detailTextLabel.text = entry.date.description } else { super.observeValueForKeyPath(keyPath, ofObject: object, change: change, context: context) } }
31. Key-Value-Observing // e.g. with ReactKit (self.textLabel!, "text") <~ KVO.stream(self, "entry.title") (self.detailTextLabel!, "text") <~ KVO.stream(self, "entry.date") |> map { $0!.description as NSString }
32. Fundament for ⚗Reactive Apps
33. The Reactive Manifesto • Responsive • Resilient • Elastic • Message Driven
34. Demo
35. try! questions.map { try $0.answer() }
36. Thanks for your attention! @mrackwitz mr@realm.io