从Firebase Flutter获取文档ID

Question

I trying to get the new created document id after data has been stored to firebase database, but get error

E/flutter (20333): [ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: NoSuchMethodError: The method 'listen' was called on null.
E/flutter (20333): Receiver: null
E/flutter (20333): Tried calling: listen(Closure: (String) => void)

send_data_bloc

 _repository
          .addOrder(order)
          .listen((documentId) => print(documentId));

repository

@override
  Observable<String> addOrder(Order order) {
      var a = endpoints.collectionEndpoint.add(order.toJson());
      a.then((val) {
        return Observable.fromFuture(val.documentID());
      });

endpoints

  @override
  get collectionEndpoint => _firestore
      .collection(collectionName)
      .document(this.id)
      .collection(orderCollectionName);

Answer 1

Here

a.then((val) {
        return Observable.fromFuture(val.documentID());
});

you are returning the observable within the then function, i believe this is not the expected behavior.

One thing you should do to improve your code quality and readability is to just user async/await. The function on the repository can be rewrited like that:

@override
Observable<String> addOrder(Order order) async {
  var documentID = await endpoints.collectionEndpoint.add(order.toJson());
  return Observable.fromFuture(val.documentID());

Try this. This should do the trick.

Answer 2

Whats the reason why you are using Observables? Is this a firebase thing?

You could adjust to:

final var documentId = await _repository.addOrder(order);
print(documentId)

Answer 3

Ideally you should return the future from the repository and await for the future on the bloc. Let me try to give a full code snippet here. It would be something like this:

send_data_bloc

final documentId = await _repository
      .addOrder(order);
print(documentId);
return documentId;

repository

@override
Future<String> addOrder(Order order) {
  return endpoints.collectionEndpoint.add(order.toJson());

endpoints

@override
get collectionEndpoint => _firestore
  .collection(collectionName)
  .document(this.id)
  .collection(orderCollectionName);

Answer 4

i had the same problem here is a snippet of how i approached it

//notice im using add while referencing the document reference

final DocumentReference documentReference=await Firestore.instance.collection('jobs').add({

      'jobid':"",
    });

then get your id from documentReference

final String jobIdd=documentReference.documentID;

after getting the id now you can add your document to cloud firestore

Firestore.instance.collection('jobs').document(jobIdd).setData({
       'category': category,          
      'description': description,
      'datePosted': formattedDate,
      'postedby': userid,
      'jobid':jobIdd,
    });