Send Push Notification to Specific Device or User via NotificationHub - swift

Question

I have implemented the notificationhub service for Apple Push Notification (APNS) and I could able to send push notification to device successfully.
I am wondering where registrationId is stored in Azure, also how could I able to send push notification to specific device or user.
In the given following notificationhub tutorial, it is being used tag, but I am not sure if I use tag for each user or device is a right approach?
let tags = ["12345"]
https://learn.microsoft.com/en-us/azure/notification-hubs/ios-sdk-swift-rest

Answer 1

Tags can be utilized to essentially create target audiences for receiving a notification. A common enough use of tags is to target devices based on country, for example. So then you could have a tag like:
let tags = ["United States"]
or
let tags = ["Poland"]
This would require the country to be detected by code on the device and then calling the SDK to store that tag.
Tags are just opaque strings, though. So you can use them in whatever way you want. For example, you could also use them to target individual users across multiple devices.
let tags = ["myuser#foo.bar"]
Use tags that best allow you to target the audience you want to target. There are limits to tags though, you can only have 60 per device registration.
You can send to a particular tag (or a combination of tags called a tag expression) using the send API and providing a tag expression. There is a documented example of this available here: https://learn.microsoft.com/en-us/azure/notification-hubs/notification-hubs-tags-segment-push-message
And the actual API docs for it: https://learn.microsoft.com/en-us/rest/api/notificationhubs/send-apns-native-notification
You would be triggering the call to this API through some server-side component of your application and most likely not from the device itself.