swift - Firebase UID vs document-id and Firestore Rules

Question

Hi I am getting a little bit confused here with Firebase User UID and Firestore Document ID (userId???)... and looking for some help :-)

By creating a user I get a UID and I write it to the database

 let db = Firestore.firestore()
 db.collection("user").addDocument(data: [
 "name": "confused",
 "uid": result!.uid ])

by doing so I get a unique document-id (marked green) which I thought is the userId as well:

The thing I wanted to achieve is that the user can only read and write his document (green) and not the other documents (red)

Therefore I used the following rules

rules_version = '2';
service cloud.firestore {
  match /databases/{database}/documents {
    // Make sure the uid of the requesting user matches name of the user
    // document. The wildcard expression {userId} makes the userId variable
    // available in rules.
    match /user/{userId} {
      allow read, update, delete: if request.auth.uid == userId;
      allow create: if request.auth.uid != null;
    }
  }
}

So the UID and the document ID (userId???) should have a connection do they? But I don't really get it?! In my app I want to retrieve the document id of the user, to use it later on a http-trigger but I can only get the UID

print(Auth.auth().currentUser!.uid)

any ideas or do I get it completely wrong?

Answer 1

Waitting for answers