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Link User Identities - Swift SDK

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  • Overview
  • Example
  • Async/Await Example

Atlas App Services provides many authentication providers to log users into your app. Each provider creates a unique user identity. App Services and the Realm Swift SDK lets you merge multiple credentials into one user identity.

Consider an application that offers anonymous login. This allows users to explore the app without registering. If users like the application, they create permanent accounts. They sign up with SSO or email/password authentication. By default, this creates a new User object. The app must link the new identity with the original User.

You can link identities using linkUser(credentials:Credentials). This links authentication providers to a logged-in User object.

New in version 10.16.0.

The Realm Swift SDK provides an async/await version of User.linkUser.

let app = App(id: YOUR_APP_SERVICES_APP_ID)
func logInAnonymously() async throws -> User {
let anonymousUser = try await app.login(credentials: Credentials.anonymous)
// User uses app, then later registers an account
let newAccountLinkedUser = try await registerNewAccount(anonymousUser: anonymousUser)
return newAccountLinkedUser
func registerNewAccount(anonymousUser: User) async throws -> User {
let email = ""
let password = "ganondorf"
try await app.emailPasswordAuth.registerUser(email: email, password: password)
// Successfully created account, now link it
// with the existing anon user
let linkedUser = try await link(user: anonymousUser, with: Credentials.emailPassword(email: email, password: password))
return linkedUser
func link(user: User, with credentials: Credentials) async throws -> User {
try await user.linkUser(credentials: credentials)
do {
let linkedUser = try await logInAnonymously()
print("Successfully linked user async: \(linkedUser)")
} catch {
print("Failed to link user: \(error.localizedDescription)")

Starting with Realm Swift SDK Versions 10.15.0 and 10.16.0, many of the Realm APIs support the Swift async/await syntax. Projects must meet these requirements:

Swift SDK Version
Swift Version Requirement
Supported OS
Swift 5.6
iOS 13.x
10.15.0 or 10.16.0
Swift 5.5
iOS 15.x

If your app accesses Realm in an async/await context, mark the code with @MainActor to avoid threading-related crashes.

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