I need to add field to document when key is the Firebase/Firestore server timestamp. The only working solution i found till now is first create record with timestamp as value with FieldValue.serverTimestamp(), than read it from Firestore and than use received value for a key. This solution looks ugly and I don’t think it is correct one.

Using FieldValue.serverTimestamp().toString() as key, add “FieldValue(Instance of ‘MethodChannelFieldValue’)”string instead of actual timestamp value.

The code looks like:

saveUserAnswersToFirestore(List<RemoteAnswerModel> answers) async {
User? user = FirebaseAuth.instance.currentUser;

DocumentReference<Map<String, dynamic>> userAnswerDoc = FirebaseFirestore.instance
    .collection('answers')
    .doc('${user?.phoneNumber}');

final now = '${Timestamp.now().millisecondsSinceEpoch}'; //FieldValue.serverTimestamp().toString();
var answersMap = answers.map((e) => e.toJson()).toList();
try {
  await userAnswerDoc.update({
    now : answersMap
  });
} catch (e) {
  await userAnswerDoc.set({
    now : answersMap
  });
}

}

Any thoughts?

This is how the result should look like: