Get only documents in a FireBase collection that have an id matching with documents in a separate collection

user_14456585 0
Viewed 139

I have the following database structure:

users
 |_____user01
          |_____groups
                   |_____0002
                   |_____0004
                   |_____0006
groups
 |_____0001
 |_____0002
 |_____0003
 |_____0004
 |_____0005
 |_____0006

I currently have a StreamBuilder() that creates a list with all the entries it finds in root/groups, so it creates a list of 6 elements.

I need it to create a list using the entries in root/groups as it's doing now, but only those that have an id that matches the IDs of entries present in root/users/user01/groups, so it should create a list with 3 elements (0002, 0004 and 0006).

I can't wrap my head around how to achieve that.

This is my StreamBuild() :

StreamBuilder(

              stream: FirebaseFirestore.instance.collection("groups").snapshots(),
              builder: (context, snapshots) {
                if (snapshots.hasData) {
                  return ListView.builder(
                      shrinkWrap: true,
                      itemCount: snapshots.data.documents.length,
                      itemBuilder: (context, index) {
                        DocumentSnapshot documentSnapshot =
                        snapshots.data.documents[index];
                        return Dismissable( 
                          child: Card(
                            )
)

Should I make a firebase query using where() that excludes documents IDs not shared by the two collections and feed the results to the StreamBuilder?

google-cloud-firestore firebase dart flutter
1 Answers

I would recommend you to use a FutureBuilder for every document inside the list you are creating using StreamBuilder and rendering using ListView.builder.

Create a future that matches each and every document in the list with documents inside the sub-collection of user i.e, groups.

Future<bool> matchDocs(String id)async{
    
    
    final result = await FirebaseFirestore.instance.collection('users').doc(FirebaseAuth.instance.currentUser.uid).collection('groups').doc(id).get();
    
    return result.exists;
  }

Inside itemBuilder function return a FutureBuilder.

StreamBuilder(
              stream:
                  FirebaseFirestore.instance.collection("groups").snapshots(),
              builder: (context, snapshots) {
                if (snapshots.hasData) {
                  return ListView.builder(
                      shrinkWrap: true,
                      itemCount: snapshots.data.documents.length,
                      itemBuilder: (context, index) {
                        DocumentSnapshot documentSnapshot =
                            snapshots.data.documents[index];
                        return FutureBuilder<bool>(
                            future: matchDocs(
                                snapshots.data.documents[index].data()['id'].toString()),
                            builder: (context, snapshot) {
                              if (snapshot.hasData) {
                                if (snapshot.data) {
                                  return Dismissible(key: null, child: null);
                                }
                              }
                             return Container();
                            } 
                         );
                      }
                   );
                }
              }
 )

Note: I did not have any idea about your exact data models, so you should be careful while implementing this solution.

user_102853440
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