Cloud Firestore Firebase Collection ref 上的 IN 查询是否有 Flutter/Dart 等价物？

Question

I want to query a Firebase collection reference with a list of multiple document IDs within a Streambuilder, but it appears the only

.where()

query functions available are:

Query where(String field, {dynamic isEqualTo, dynamic isLessThan, dynamic isLessThanOrEqualTo, dynamic isGreaterThan, dynamic isGreaterThanOrEqualTo, dynamic arrayContains, bool isNull})

I have tested isEqualTo and this works fine if I set a string to pass in, but I can't get this to work with a list. It appears there is an IN function in the official Firebase documentation which would provide this function, to a maximum of 10 items:

https://firebase.google.com/docs/firestore/query-data/queries#in_and_array-contains-any

Is there an equivalent IN function in Flutter or another way to achieve this? The list I am trying to pass in is actually served by a parent Streambuilder, which queries a User collection for the specific user and passes in all groups to the second Streambuilder:

class _StarredChatState extends State<StarredChat> {

final _firestore = Firestore.instance;
  @override
  Widget build(BuildContext context) {
    final user = Provider.of<User>(context);
    final userID = user.uid;   
    return StreamBuilder<QuerySnapshot>( 
      stream: _firestore.collection('users/$userID/chats')
                        .snapshots(),
      builder: (context, snapshot) {
        if (!snapshot.hasData) {
          return Center(
            child: CircularProgressIndicator(
              backgroundColor: Colors.lightBlueAccent,
            ),
          );
        }
        List<String> ChatIDList = [];
        final ChatIDs = snapshot.data.documents;
        for(var x in ChatIDs) {
          final ChatID = x.data['chats'].toString();
          ChatIDList.add(ChatID);
        }

        return StreamBuilder<QuerySnapshot>(
          stream: _firestore.collection('chatrooms')
                            // here is where I need the IN operator as neither
                            // arraycontains or isEqualTo give the desired result
                            .where('description', arrayContains: ChatIDList)
                            .snapshots(),
          builder: (context, snapshot) {

          if (!snapshot.hasData) {
          return Center(
            child: CircularProgressIndicator(
              backgroundColor: Colors.lightBlueAccent,
            ),
          );
        }
          //Here is where I want to return a ListBuilder for the above returned 
          //Streambuilder list

          }

          );


      }
    );
  }
}

My other attempt has been to include all users who have joined a chatroom as a subcollection within the individual chat document, but as these have unique autoID's I'm not able to generate a stream of all chats with my specific user as I can't pass in a full path to the nested subcollection. Any other pointers would be really appreciated.

Thanks

Answer 1

My guess is that you're on an older version of FlutterFire's cloud_firestore plugin, as the whereIn operator is definitely present in the current version of the library. See the reference docs here .

You might want to upgrade to the latest version of FlutterFire, to get the operator.