How to get a CloudFirestore nested collection into the ExpasionTile childrens?

[jobel...@gmail.com]

Hello, 

I cannot figure it out how to retrieve a nested collection in CloudFirestore and use the nested collection to create the childrens of a ExpansionTile.

The basic structure of CloudFirebase is:

Collection projects: 

 - name

- Collection surveys:

   - surveyName

   - Collection stations:

       - name

       - geopoint

I want to show  within the `ExpansionTile` , the project `name` as title, and childrens all the surveys using their name in the ListTile.

Any help would be much aprecciated!

class SurveysItems {
  final String surveyName;
  final String surveyKey;
  const SurveysItems({this.surveyName, this.surveyKey});
  factory SurveysItems.fromDocument(DocumentSnapshot document) {
    return SurveysItems(
        surveyName: document['surveyName'], surveyKey: document.documentID);
  }
}

class ProjectItem {
  final String name;
  final String projectKey;
  const ProjectItem({this.name, this.projectKey});
  factory ProjectItem.fromDocument(DocumentSnapshot document) {
    return ProjectItem(
      name: document['name'],
      projectKey: document.documentID,
    );
  }
}

class StationItems {
  final String name;
  final String stationKey;
  const StationItems({this.name, this.stationKey});
  factory StationItems.fromDocument(DocumentSnapshot document) {
    return StationItems(
        name: document['name'], stationKey: document.documentID);
  }
}

class ProjectList extends StatelessWidget {
  ProjectList({this.firestore});

  final Firestore firestore;

  @override
  Widget build(BuildContext context) {
    return StreamBuilder<QuerySnapshot>(
      stream: firestore.collection('projects').snapshots(),
      builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
        if (!snapshot.hasData) return const Text('Loading...');
        final int projectsCount = snapshot.data.documents.length;
        return new ListView.builder(
          itemCount: projectsCount,
          itemBuilder: (_, int index) {
            final DocumentSnapshot document = snapshot.data.documents[index];
            //final CollectionReference surveysCollection = document.reference.collection('surveys');
            final ProjectItem projectItem = ProjectItem.fromDocument(document);

            Future<List<SurveysItems>> surveyItems =  document.reference.collection('surveys').getDocuments()
                .then((docs){

                  return docs.documents.map(
                          (d){ SurveysItems.fromDocument(d); }).toList();

                });

            return ExpansionTile(
              title: Text(projectItem.name),
              // the following line does not work as the method map does not exist for the Future.
              children: surveyItems.map((SurveysItems item){ return ListTile(title: Text(item.surveyName),); }).toList());


          },
        );
      },
    );
  }
}

[jobel...@gmail.com]

I found my solution, I assume there would be more elegant solutions, but the main piece that I was missing was:

List<Widget> surveysList = [];
              documents.forEach((doc) {
                PageStorageKey _surveyKey =
                    new PageStorageKey('${doc.documentID}');

                surveysList.add(ListTile(
                  key: _surveyKey,
                  title: Text(doc['surveyName']),
                ));
              });
              return Column(children: surveysList);
            })

Final implementation:

class ProjectList extends StatelessWidget {
  ProjectList({this.firestore});

  final Firestore firestore;

  @override
  Widget build(BuildContext context) {
    return StreamBuilder<QuerySnapshot>(
      stream: firestore.collection('projects').snapshots(),
      builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
        if (!snapshot.hasData) return const Text('Loading...');

        //final int projectsCount = snapshot.data.documents.length;
        List<DocumentSnapshot> documents = snapshot.data.documents;
        return ExpansionTileList(
          firestore: firestore,
          documents: documents,
        );
      },
    );
  }
}

class ExpansionTileList extends StatelessWidget {
  final List<DocumentSnapshot> documents;
  final Firestore firestore;

  ExpansionTileList({this.documents, this.firestore});

  List<Widget> _getChildren() {
    List<Widget> children = [];
    documents.forEach((doc) {
      children.add(
        ProjectsExpansionTile(
          name: doc['name'],
          projectKey: doc.documentID,
          firestore: firestore,
        ),
      );
    });
    return children;
  }

  @override
  Widget build(BuildContext context) {
    return ListView(
      children: _getChildren(),
    );
  }
}

class ProjectsExpansionTile extends StatelessWidget {
  ProjectsExpansionTile({this.projectKey, this.name, this.firestore});

  final String projectKey;
  final String name;

  final Firestore firestore;

  @override
  Widget build(BuildContext context) {

    PageStorageKey _projectKey = PageStorageKey('$projectKey');

    return ExpansionTile(
      key: _projectKey,
      title: Text(
        name,
        style: TextStyle(fontSize: 28.0),
      ),
      children: <Widget>[
        StreamBuilder(
            stream: firestore
                .collection('projects')
                .document(projectKey)
                .collection('surveys')

                .snapshots(),
            builder:
                (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
              if (!snapshot.hasData) return const Text('Loading...');

              //final int surveysCount = snapshot.data.documents.length;
              List<DocumentSnapshot> documents = snapshot.data.documents;

              List<Widget> surveysList = [];
              documents.forEach((doc) {
                PageStorageKey _surveyKey =
                    new PageStorageKey('${doc.documentID}');

                surveysList.add(ListTile(
                  key: _surveyKey,
                  title: Text(doc['surveyName']),
                ));
              });
              return Column(children: surveysList);
            })
      ],
    );
  }
}

Cheers!

Happy coding!