Sync Data¶

Prerequisites¶

Before you can access a synced realm from the client, you must:

• Enable sync in the Realm UI.
• Initialize the app and authenticate a user in your client project.

Open a Synced Realm¶

To open a synced realm for a given partition value, initialize a Realm with a configuration object generated by passing the partition value to the authenticated user's configuration method:

let realm = try! Realm(configuration: configuration)
print("Opened realm: \(realm)")

If it is the first time opening that particular realm, especially if it is a read-only realm, use the Realm.asyncOpen() method instead:

let app = App(id: YOUR_REALM_APP_ID)
// Log in...
let user = app.currentUser
let partitionValue = "some partition value"
var configuration = user!.configuration(partitionValue: partitionValue)
Realm.asyncOpen(configuration: configuration) { result in
    switch result {
    case .failure(let error):
        print("Failed to open realm: \(error.localizedDescription)")
        // handle error
    case .success(let realm):
        print("Successfully opened realm: \(realm)")
        // Use realm
    }
}

The partition value specifies which subset of your data to sync. This is typically a user ID, project ID, store ID, or some other category identifier in your app that has particular relevance to the current user.

Sync Data¶

The syntax to read, write, and watch for changes on a synced realm is identical to the syntax for non-synced realms. While you work with local data, a background thread efficiently integrates, uploads, and downloads changesets.

The following code reads a collection of Task objects, watches that collection for changes, then writes a new Task to the realm:

// Read all tasks in the realm. No special syntax required for synced realms.
let tasks = realm.objects(Task.self)
// Watch for changes. No special syntax required for synced realms.
// Retain notificationToken as long as you want to observe.
let notificationToken = tasks.observe { (changes) in
     print("Changed: \(changes)")
}
// Write to the realm. No special syntax required for synced realms.
try! realm.write {
  realm.add(Task(partition: partitionValue, name: "My task"))
}
// Later, when done observing
notificationToken.invalidate()

Summary¶

• Open a synced realm with the configuration object generated when you pass a partition value to the user object's configuration method.
• Compared to using a non-synced realm, there is no special syntax for reading from, writing to, or watching objects on a synced realm.
• You should avoid writing to a synced realm on the main thread.