How to customize Notification in Lock screen swift

Question

I see the Telegram application uses the first letter of the contact name to replace the Logo of the app. How can I do that?

I try to search but not found

Answer 1

From reading the documentation, I think they are using the avatar in:

Communication notifications provide a rich experience for direct communications. These notifications have a distinct user experience that features prominent avatars and group names.

https://developer.apple.com/documentation/usernotifications/implementing_communication_notifications

Apple has provided auto-images generated from the contact name, the convention is to use [first initial] | [last initial].

A single "A" would be someone with firstname-only, or lastname-only thet starts with "A" or "a".