Xamarin.iOS send data from iOS project to Notification Service Extension - xamarin

Question

In Xamarin.iOS project I am intercepting the push notification and I want to modify it before presenting to the user according to some conditions that are accessible (stored preferences) in the iOS project. How can I pass data from iOS project to the Notification Service Extension, and potentially the other way around as well? Or maybe more precisely, how can I access user preferences from the Xamarin.Forms project in the iOS Notification Service Extension project?
I am mostly interested in accessing user preferences that I stored using Xamarin.Essentials
This is the template code for the Notification Service Extension:
namespace NotifServiceExtension
{
[Register("NotificationService")]
public class NotificationService : UNNotificationServiceExtension
{
Action<UNNotificationContent> ContentHandler { get; set; }
UNMutableNotificationContent BestAttemptContent { get; set; }
protected NotificationService(IntPtr handle) : base(handle)
{
// Note: this .ctor should not contain any initialization logic.
}
public override void DidReceiveNotificationRequest(UNNotificationRequest request, Action<UNNotificationContent> contentHandler)
{
ContentHandler = contentHandler;
BestAttemptContent = (UNMutableNotificationContent)request.Content.MutableCopy();
// Modify the notification content here...
var region = Preferences.Get("region_key", "error"); // I cannot access preferences this way
BestAttemptContent.Title = string.Format("{0}[modified]", BestAttemptContent.Title);
ContentHandler(BestAttemptContent);
}
public override void TimeWillExpire()
{
// Called just before the extension will be terminated by the system.
// Use this as an opportunity to deliver your "best attempt" at modified content, otherwise the original push payload will be used.
ContentHandler(BestAttemptContent);
}
}
}

Answer 1

The simplest way to do this is by exposing a method on the Xamarin.Forms App class.
In the App.xaml.cs file add a new method like this:
public string GetUserRegion()
{
return Preferences.Get("region_key", "error");
}
and inside your NotificationService class you can get the region like this:
var region = (Xamarin.Forms.Application.Current as App)?.GetUserRegion();