How to get cloud firestore document unique Id before adding data to cloud firestore as Realtime data-CodePudding

We can get pushed Key in realtime database before adding data but in cloud firestore I could not find any method to find unique key before adding data.

String uniqueKey = ref.push().getKey();

So I am doing two operation add and then update .If I can get unique key before adding data to firestore I can do it one operation just add with unique key included in the document.

Currently I am doing like this.

Collection Reference

final sitesRef = FirebaseFirestore.instance
      .collection('book_mark')
      .doc(getUserId())
      .collection("link")
      .withConverter<SiteModel>(
        fromFirestore: (snapshots, _) => SiteModel.fromJson(snapshots.data()!),
        toFirestore: (siteModel, _) => siteModel.toJson(),
      );

Add document then get document Id from response then update the document with document Id.So if update operation is failed somehow I could not access the document anymore. So it will create a problem down the line.

Future<String> addSiteFireStore(SiteModel siteModel) async {
    try {
      DocumentReference<SiteModel> response = await sitesRef.add(siteModel);
      final Map<String, dynamic> data = <String, dynamic>{};
      data['docId'] = response.id;
      sitesRef.doc(response.id).update(data);
      _logger.fine("Link added successfully");
      return "Link added successfully";
    } on Exception catch (_) {
      _logger.shout("Could not add link.Please try again");
      return "Could not add link.Please try again";
    }
  }

Is there any way to get the document Id beforehand? Thanks in advance.

CodePudding user response：

You can get a new document reference without writing to it by calling doc() (without arguments) on a CollectionReference. Then you can get the id property from the new document reference, similar to how you call getKey() on the new RTDB reference.

So:

final newRef = FirebaseFirestore.instance
      .collection('book_mark')
      .doc();
final newId = newRef.id;

Also see the FlutterFire documentation on CollectionReference.doc().