Apple Sign-In Button with MAUI Embedding in Uno

In Uno Platform projects, implementing a "Sign in with Apple" Button is possible through MAUI embedding (more on which in our Overview). Below is a simple example of how you can add the Apple Sign-In Button to your project. We will inject it into the visual tree from the code-behind and handle the authorization using Apple's Authentication Services.

General Usage

Activate the Apple Sign-In Capability:
- If you are using Visual Studio, open the Entitlements.plist file and locate the "Sign In With Apple" checkbox. After checking it, ensure you save your changes.
- Alternatively, you can open the Entitlements.plist file in any text editor and add the following within the <dict> tag:
```
<key>com.apple.developer.applesignin</key>
<array>
    <string>Default</string>
</array>
```

Import Necessary Namespaces:

using AuthenticationServices;
using Foundation;
using UIKit;

In the constructor of your Page or control, create the Apple Sign-In Button:

Important

Ensure that you wrap platform-specific code in #if __IOS__ directives. For more details, refer to the Platform-specific C# documentation.
```
var appleSignInButton = new ASAuthorizationAppleIdButton(ASAuthorizationAppleIdButtonType.Default, ASAuthorizationAppleIdButtonStyle.WhiteOutline);
appleSignInButton.TouchUpInside += HandleAuthorizationAppleIDButtonPress;
appleSignInButton.CornerRadius = 50;

// Retain the delegate to prevent garbage collection
_appleSignInDelegate = new AuthorizationControllerDelegate(this);
```
Note

It's important to retain a reference to the delegate (_appleSignInDelegate) to avoid garbage collection issues. This ensures that the authorization process is completed without interruption.

Inject the Apple Sign-In button into the visual tree using VisualTreeHelper.AdaptNative:

var adaptedAppleButton = VisualTreeHelper.AdaptNative(appleSignInButton);
var borderWrapper = new Border
{
    MinHeight = 50,
    MinWidth = 250,
    HorizontalAlignment = HorizontalAlignment.Center,
    Child = adaptedAppleButton,
};

m_MainStackPanel.Children.Add(borderWrapper);

Handle the button's TouchUpInside event to initiate Apple Sign-In:

private void HandleAuthorizationAppleIDButtonPress(object sender, EventArgs e)
{
    var appleIDProvider = new ASAuthorizationAppleIdProvider();
    var request = appleIDProvider.CreateRequest();
    request.RequestedScopes = new[] { ASAuthorizationScope.FullName, ASAuthorizationScope.Email };

    var authorizationController = new ASAuthorizationController(new ASAuthorizationRequest[] { request });
    authorizationController.Delegate = _appleSignInDelegate;  // Use the retained delegate
    authorizationController.PresentationContextProvider = new PresentationContextProvider();  // Set the presentation context provider
    authorizationController.PerformRequests();
}

Custom Delegate for Authorization

To handle the result of the sign-in process, create a custom delegate:

public class AuthorizationControllerDelegate : ASAuthorizationControllerDelegate
{
    private readonly MyUserControl _parent;

    public AuthorizationControllerDelegate(MyUserControl parent)
    {
        _parent = parent;
    }

    public override void DidComplete(ASAuthorizationController controller, ASAuthorization authorization)
    {
        System.Diagnostics.Debug.WriteLine("Authorization successful.");

        try
        {
            var appleIdCredential = authorization.GetCredential<ASAuthorizationAppleIdCredential>();

            var userIdentifier = appleIdCredential?.User;
            // Handle successful authorization, retrieve user details
        }
        catch (Exception ex)
        {
            System.Diagnostics.Debug.WriteLine($"Authorization failed: {ex.Message}");
        }
    }
}

Managing Delegate in MVVM

If you're using an MVVM architecture, the delegate should handle sign-in logic indirectly by passing the necessary data to the ViewModel. This keeps the code clean and follows MVVM principles. For example:

Instead of passing the user control (MyUserControl) to the AuthorizationControllerDelegate, pass a reference to the ViewModel or a dedicated service.
In the delegate, you can call methods on the ViewModel to handle the authorization flow, such as storing user information or navigating to another page.

Example:

public class AuthorizationControllerDelegate : ASAuthorizationControllerDelegate
{
    private readonly MyViewModel _viewModel;

    public AuthorizationControllerDelegate(MyViewModel viewModel)
    {
        _viewModel = viewModel;
    }

    public override void DidComplete(ASAuthorizationController controller, ASAuthorization authorization)
    {
        System.Diagnostics.Debug.WriteLine("Authorization successful.");

        try
        {
            var appleIdCredential = authorization.GetCredential<ASAuthorizationAppleIdCredential>();
            var userIdentifier = appleIdCredential?.User;

            // Pass the user info to the ViewModel for further processing
            _viewModel.HandleSuccessfulAuthorization(userIdentifier);
        }
        catch (Exception ex)
        {
            System.Diagnostics.Debug.WriteLine($"Authorization failed: {ex.Message}");
        }
    }
}

Presentation Context Provider

For proper handling of the presentation context on iOS, implement a PresentationContextProvider:

public class PresentationContextProvider : NSObject, IASAuthorizationControllerPresentationContextProviding
{
    public UIWindow GetPresentationAnchor(ASAuthorizationController controller)
    {
        return UIApplication.SharedApplication.KeyWindow;
    }
}

More Resources

For more details on platform-specific considerations or to improve the user experience: