⚗ Reactive Programming with Realm 

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What is Realm & How does it work? 

What is Realm not? 

Realm is not an ORM. Realm is the database itself. 

Embedded NoSQL Object-oriented Database 

Embedded = Built from scratch for ! 

⚡ SQLite 

NoSQL = Schema-free? No, too slow. ! 

Object-oriented 

class Person : Object { dynamic var name = "" dynamic var age = 0 let children = List() let parents = LinkingObjects(fromType: Person.self, property: "children") } 

You directly interact with memory-mapped data. 

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; } } 

Their classes describe how to read from there and navigate within the file. 

But let's take a closer look how the data structure looks like. 

Realm !"" Versions !"" Tables !"" Columns !"" Values 

The root level describes the different versions ! " # 

ACID • Atomicity • Consistency • Isolation • Durability 

Naïve 

Multi Version Concurrency Control 

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Copy-on-Write 

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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 ! 

Built-in Notifications • File-wide Observation • Fine-grained Notifications on Collections • Key-Value-Observing compliant 

File-wide Observation // Observe Realm Notifications let token = realm.addNotificationBlock { notification, realm in viewController.updateUI() } // later token.stop() 

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 } } 

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) { 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) } } 

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 } 

Fundament for ⚗Reactive Apps 

The Reactive Manifesto • Responsive • Resilient • Elastic • Message Driven 

Demo 

try! questions.map { try $0.answer() } 

Thanks for your attention! @mrackwitz [email protected]