I have the problem with updating the documentUid as in array at the same time which I get a snapShot from here
var userDocumentUid = snapshot.data?["membersUid"]; But it says list' can't be assigned to the parameter type 'string?'. Here .doc(userDocumentUid??[])

Full code:

    StreamBuilder(
              stream: FirebaseFirestore.instance
                  .collection("groups")
                  .doc(groupId)
                  .snapshots(),
              builder: (context, AsyncSnapshot<DocumentSnapshot> snapshot) {
              //get array snapShot as show in img