how to fetch data from firestore array of a document with flutter?

Question

this is my users collection in cloud fire store:

this is the function that gets users from users collection in firestore

 Stream<QuerySnapshot> fetchUsersInSearch() {
    return Firestore.instance.collection('users').snapshots();
  }

i use this method

  final emailResults = snapshot.data.documents
              .where((u) => u['email'].contains(query));

in the following streamBuilder to fetch users by their email.

i have this streamBuilder to populate the data on screen

return StreamBuilder<QuerySnapshot>(
        stream: DatabaseService().fetchUsersInSearch(),
        builder: (context, AsyncSnapshot<QuerySnapshot> snapshot) {

          final emailResults = snapshot.data.documents
              .where((u) => u['email'].contains(query));

          if (!snapshot.hasData) {
            return Container(
              color: Theme.of(context).primaryColor,
              child: Center(
                child: Text(
                  '',
                  style: TextStyle(
                      fontSize: 16, color: Theme.of(context).primaryColor),
                ),
              ),
            );
          }
          if (emailResults.length > 0) {
            return Container(
              color: Theme.of(context).primaryColor,
              child: ListView(
                children: emailResults
                    .map<Widget>((u) => GestureDetector(
                          child: Padding(
                            padding: const EdgeInsets.all(0.1),
                            child: Container(
                              padding: EdgeInsets.symmetric(vertical: 5),
                              decoration: BoxDecoration(
                                  color: Theme.of(context).primaryColor,
                                  border: Border(
                                      bottom: BorderSide(
                                          width: 0.3, color: Colors.grey[50]))),
                              child: ListTile(
                                leading: CircleAvatar(
                                        backgroundColor:
                                            Theme.of(context).primaryColor,
                                        backgroundImage:
                                            NetworkImage(u['userAvatarUrl']),
                                        radius: 20,
                                      ),
                                title: Container(
                                  padding: EdgeInsets.only(left: 10),
                                  child: Column(
                                    crossAxisAlignment:
                                        CrossAxisAlignment.start,
                                    children: [
                                      Text(u['email'],
                                          style: TextStyle(
                                              fontSize: 16,
                                              color: Theme.of(context)
                                                  .accentColor),
                                          overflow: TextOverflow.ellipsis),
                                      SizedBox(
                                        height: 5,
                                      ),
                                
                                    ],
                                  ),
                                ),
                                
                              ),
                            ),
                          ),
                          onTap: () {
                            showUserProfile(u['id']);
                          },
                        ))
                    .toList(),
              ),
            );
          } else {
            return Container(
              color: Theme.of(context).primaryColor,
              child: Center(
                child: Text(
                  'No results found',
                  style: TextStyle(
                    fontSize: 16,
                    color: Theme.of(context).accentColor,
                  ),
                ),
              ),
            );
          }
        });

this is working perfectly and fetching users inside a listView by their email...

p.s: the (query) is a string i type in a seach bar.

how can i make a query to fetch users by their otherUsernames...the second field in the screenshot of the users collection ?!

i tried this:

  final otherUsernamesResults = snapshot.data.documents
              .where((u) => u['otherUsernames'].contains(query));

but its returning this error:

The method 'contains' was called on null.
Receiver: null
Tried calling: contains("#username1")

what am i doing wrong here ?!!

any help would be much appreciated..

Vishnubly · Accepted Answer · 2021-02-09 17:36:07Z

1

Try this:-

Stream<QuerySnapshot> getUsers() {
  final usersCollection = FirebaseFirestore.instance.collection('users');
  return usersCollection.where('otherUsernames', arrayContainsAny: ['username1', 'username2']);
}

For firestore version 0.16.0

answered Feb 9, 2021 at 17:36

Vishnubly

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1 Comment

mohamed mostapha Over a year ago

i made some corrections to your answer to make it work: Stream<QuerySnapshot> getUsers() { final usersCollection = Firestore.instance.collection('users').snapshots(); return usersCollection.where('otherUsernames', arrayContainsAny: ['username1', 'username2']); } but at least the the approach made me happy that we can search for users by sub collections

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