Lesson 12 - iOS ToDo app in Swift - Database migrations and sorting
In the previous lesson, iOS ToDo app in Swift - Custom TableViewCell, we added task priorities to our ToDo app in Swift for iOS.
We promised to perform database migrations and learn to sort data in today's iOS development tutorial.
Realm migrations
To migrate a database basically means to modify the database schema to
correspond to the new model. It's easy to do it in Realm, we just create a code
block in AppDelegate
, specifically in the following method:
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool
Realm has a cool documentation where we can find everything needed. Our migration will look like this:
Realm.Configuration.defaultConfiguration = Realm.Configuration( schemaVersion: 1, migrationBlock: { migration, oldSchemaVersion in if (oldSchemaVersion < 1) { migration.enumerateObjects(ofType: ToDo.className()) { oldObject, newObject in newObject!["priority"] = 1 } } })
We'll place this whole block to the
...End of the preview...

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We'll learn to migrate databases of iOS apps which are already in AppStore. And also to sort and filter data (our objects) using Realm in Swift.
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