Hub

Amplify iOS v1 is now in Maintenance Mode until May 31st, 2024. This means that we will continue to include updates to ensure compatibility with backend services and security. No new features will be introduced in v1.

Please use the latest version (v2) of Amplify Library for Swift to get started.

If you are currently using v1, follow these instructions to upgrade to v2.

Amplify libraries should be used for all new cloud connected applications. If you are currently using the AWS Mobile SDK for iOS, you can access the documentation here.

Amplify has a local eventing system called Hub. It is a lightweight implementation of Publisher-Subscriber pattern, and is used to share data between modules and components in your app. Amplify uses Hub for different categories to communicate with one another when specific events occur, such as authentication events like a user sign-in or notification of a file download.

Working with the API

Listening for messages

You can use Amplify.Hub.listen(to: HubChannel) {...} (listener) or Amplify.Hub.publisher(for: HubChannel).sink {...} (Combine) to listen for messages that have been dispatched. Additionally, you can pass isIncluded: HubFilter or eventName: HubPayloadEventName to the listen method to further filter Hub events. You can add multiple listeners to your application for different combinations of channels, filters, and events.

1override func viewDidLoad() {
2    super.viewDidLoad()
3    // Do any additional setup after loading the view.
4
5    // Assumes `unsubscribeToken` is declared as an instance variable in your view
6    unsubscribeToken = Amplify.Hub.listen(to: .auth) { payload in
7        switch payload.eventName {
8        case HubPayload.EventName.Auth.signedIn:
9            print("User signed in")
10            // Update UI
11
12        case HubPayload.EventName.Auth.sessionExpired:
13            print("Session expired")
14            // Re-authenticate the user
15
16        case HubPayload.EventName.Auth.signedOut:
17            print("User signed out")
18            // Update UI
19
20        case HubPayload.EventName.Auth.userDeleted:
21            print("User deleted")
22            // Update UI
23
24        default:
25            break
26        }
27    }
28}

1override func viewDidLoad() {
2    super.viewDidLoad()
3    // Do any additional setup after loading the view.
4
5    // Assumes `sink` is declared as an instance variable in your view controller
6    sink = Amplify.Hub
7        .publisher(for: .auth)
8        .sink { payload in
9            switch payload.eventName {
10            case HubPayload.EventName.Auth.signedIn:
11                print("User signed in")
12                // Update UI
13
14            case HubPayload.EventName.Auth.sessionExpired:
15                print("Session expired")
16                // Re-authenticate the user
17
18            case HubPayload.EventName.Auth.signedOut:
19                print("User signed out")
20                // Update UI
21
22            case HubPayload.EventName.Auth.userDeleted:
23                print("User deleted")
24                // Update UI
25
26            default:
27                break
28            }
29        }
30}

Stop Listening

Hub provides a way to stop listening for messages. This is useful if you no longer need to receive messages in your application flow.

1// Assumes `unsubscribeToken` references the token
2// returned by Amplify.Hub.listen(...)
3Amplify.Hub.removeListener(unsubscribeToken)

1// Assumes `sink` references the sink
2// returned by Amplify.Hub.publisher(...).sink
3sink.cancel()