yohei SUGIGAMI Realm Centered Design RxSwift+RxRealm w/ RealmNotification Sep. 29, 2016 @ SanSan Realm meetup #19

Yohei SUGIGAMI ID susieyy TwitterˍGithub & Qiita

γΰτͰίίϩΦυϧ Launch iPhone3G iOS Developer since mid 2008

γΰτͰίίϩΦυϧ WWDC 2014 Swift Developer since Day1

γΰτͰίίϩΦυϧ Working in a Wantedly

Our issues in iOS development

Our issues in iOS development Complex

Our issues in iOS development State and data management Complex

Our issues in iOS development Asynchronous processing Complex

Our issues in iOS development Massive delegate pattern Complex https://developer.apple.com/library/content/documentation/General/Conceptual/DevPedia-CocoaCore/MVC.html Apple MVC Apple MVC

Reactive program paradigm Observable Asynchronous data streams Functional program paradigm No side effects function Immutable structure Higher-order functions Lambda expression, monads Asynchronous friendly Unidirectional Data Flow Single source of truth The approach avoids complicated to simplify Redux RxSwift Reactive Cocoa simplify

Hoping between RxSwift and ReSwift Redux Rx ??? w/ MVVM (RxSwift) (ReSwift) Unidirectional 
 Data Flow

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Approaching based on Rx with Realm Redux Rx Realm + w/ MVVM (RxSwift) (ReSwift) Unidirectional 
 Data Flow Unidirectional 
 Data Flow (RxRealm)

Realm Centered Design View ViewModel Model Rx ( Local state ) Store ( App state ) Rx w/ MVVM

Unidirectional Data Flow Transaction ( atomic ) Notification Subscribe Realm Centered Design https://realm.io/news/unidirectional-data-flow-in-swift/

Launch iPhone3G iOS Developer since mid 2008 Key technologies Realm Notification RxRealm RxSwift w/ MVVM

Launch iPhone3G iOS Developer since mid 2008 Realm Notification Notifications section https://realm.io/docs/swift/latest/#notifications Collection Notifications, since ver 0.98 https://realm.io/news/realm-objc-swift-0.98.0/ Fine-grained change notifications, since ver 0.99 https://realm.io/news/realm-objc-swift-0.99.0/

Launch iPhone3G iOS Developer since mid 2008 Do you know the Realm Notification?

Launch iPhone3G iOS Developer since mid 2008 You can be notified whenever a Realm, Results, List or LinkingObjects is updated by calling the addNotificationBlock method. a.k.a. Observe What Realm Notification

Launch iPhone3G iOS Developer since mid 2008 Realm Notifications Collection Notifications Fine-grained change Points

Launch iPhone3G iOS Developer since mid 2008 Realm instances send out notifications to other instances on other threads every time a write transaction is committed: Realm Notifications

Launch iPhone3G iOS Developer since mid 2008 Realm Notifications, e.g.

Launch iPhone3G iOS Developer since mid 2008 Collection Notifications Notified of updates to query results or to specific objects.

Launch iPhone3G iOS Developer since mid 2008 ( should keep a strong reference ) Collection Notifications, e.g.

Launch iPhone3G iOS Developer since mid 2008 Fine-grained level changing This change parameter describes including the indices of objects that have been inserted, deleted, or modified since the last notification.

Launch iPhone3G iOS Developer since mid 2008 notified indices with deltas Fine-grained change, e.g.

Launch iPhone3G iOS Developer since mid 2008 In the case of Core Data let notificationCenter = NSNotificationCenter.defaultCenter() notificationCenter.addObserver(self, selector: #selector(managedObjectContextDidChange:), name: NSManagedObjectContextObjectsDidChangeNotification,
 object: privateManagedObjectContext) Can not observe with filtering.

Launch iPhone3G iOS Developer since mid 2008 In the case of Core Data func managedObjectContextObjectsDidChange(notification: NSNotification) { guard let userInfo = notification.userInfo else { return } if let inserts = userInfo[NSInsertedObjectsKey] as? Set where inserts.count > 0 { } if let updates = userInfo[NSUpdatedObjectsKey] as? Set where updates.count > 0 { } if let deletes = userInfo[NSDeletedObjectsKey] as? Set where deletes.count > 0 { } } Received changed objects, instead of changed indices

Launch iPhone3G iOS Developer since mid 2008 Notified timing When notifications can’t be delivered instantly, multiple write transactions may be coalesced into a single notification. t Tx COMMIT Tx COMMIT Tx COMMIT Tx COMMIT Tx COMMIT t Notice Notice Write Notification

Launch iPhone3G iOS Developer since mid 2008 It is also notified being monitored relation destination of the change of the Object. Observable relations ( linking objects )

Launch iPhone3G iOS Developer since mid 2008 Observable relations ( linking objects ) UserObject name avatar_url registered deleted_at profile ProfileObject company position working_histories academy_records emails EmailObject email Observe Change Change Notified

Launch iPhone3G iOS Developer since mid 2008 Model View B View A Notification Notification WriteTx Absolutely separation logic and views Singleton PreFetch BackgroundFetch

Launch iPhone3G iOS Developer since mid 2008 View A View B Notification WriteTx Absolutely separation logic and views

e.g. WriteTx Notification Notification ➜ ➜

Launch iPhone3G iOS Developer since mid 2008 RxSwift RxRealm x meets https://github.com/RxSwiftCommunity/RxRealm

Launch iPhone3G iOS Developer since mid 2008 What RxRealm Rx wrapper for Realm's collection types.

Launch iPhone3G iOS Developer since mid 2008 Observing collections Adds to Results, List, LinkingObjects and AnyRealmCollection these methods: - asObservable() - asObservableArray() - asObservableChangeset() - asObservableArrayChangeset() returning an Observable, RealmChangeset?>

Launch iPhone3G iOS Developer since mid 2008 try! Realm().objects(ContactRealm) .asObservableChangeset() .subscribeNext { [weak self] results, changeset in guard let tableView = self?.tableView else { return } self?.results = results if let changeset = changeset { tableView.beginUpdates() tableView.insertRowsAtIndexPaths(…, withRowAnimation: .Automatic) tableView.deleteRowsAtIndexPaths(…, withRowAnimation: .Automatic) tableView.reloadRowsAtIndexPaths(…, withRowAnimation: .Automatic) tableView.endUpdates() } else { tableView.reloadData() } }.addDisposableTo(disposeBag) e.g.

- rx_add() - rx_delete() Write transactions // Simple Create [MessageRealm("hello"), MessageRealm("world")] .toObservable() .subscribe(Realm.rx_add()) // With API let request = API.Endpoint.MessagesRequest().request() Session.rx_response(request) .subscribe(Realm.rx_add())

B Launch iPhone3G iOS Developer since mid 2008 RxSwift MVVM Realm Centered Design RxRealm

Launch iPhone3G iOS Developer since mid 2008 View ViewModel View A Subscribe Holding - The state of a screen-specific (Requesting, etc) - The main data of a screen RxSwift w/ MVVM It is difficult to handle the screen cross-data. View B View C

Launch iPhone3G iOS Developer since mid 2008 View ViewModel Subscribe Singleton RxSwift w/ MVVM and Singleton Global ViewModel View A View B View C Holding - The state of a screen-specific (Requesting, etc) - The main data of a screen (Rx Variable) The state of cross over screens

Launch iPhone3G iOS Developer since mid 2008 View ViewModel Observable Store Subscribe The state of a screen-specific Singleton RxSwift+RxRealm w/ MVVM (RxRealm) View A View B View C (Rx Variable) The main data of screens The state of cross over screens

Conclusion Simple ( is not easy ) Complex

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