Accessing all docs in subbcollecions - flutter

Question

I'm having struggles for the last couple of days, so any help highly appreciates it.
I have an app where everyday users take photos of themself ( I set the date of that day as docId), then in UI, every day has a page ( a carousel) where users can swipe and see the photos belonging to every day.
I attached a screenshot of the Firstore database.
But having a problem reading images , tried every method.
P.s : When I set the DocId for instance: 2023-01-11 it works but it just show the photos of one day , I need to fetch all images from all days.
Method adding data to Firestore:
final photoToDb = db
.collection('photos')
.doc(DateFormat('yyyy-MM-dd').format(newDate))
.collection('Today Photos')
.withConverter(
fromFirestore: PhotoModel.fromFirestore,
toFirestore: ((PhotoModel photoModel, options) =>
photoModel.toFirestore()),
);
photoToDb.add(photo);
} catch (e) {
return ('errro');
}
}
Page where I'm trying to display images ,
lass SugarPhotoPage extends StatefulWidget {
const SugarPhotoPage({
super.key,
});
#override
State<SugarPhotoPage> createState() => _SugarPhotoPageState();
}
class _SugarPhotoPageState extends State<SugarPhotoPage> {
final Stream<QuerySnapshot> _photoStream = FirebaseFirestore.instance
.collection('photos')
.doc()
.collection('Today Photos')
.snapshots();
#override
void initState() {
print('${AppData.userSelectedData}');
super.initState();
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
backgroundColor: Colors.transparent,
elevation: 0,
),
body: StreamBuilder<QuerySnapshot>(
stream: _photoStream,
builder: (context, snapshot) {
if (snapshot.hasError) {
return const Text('Something went wrong');
}
if (snapshot.connectionState == ConnectionState.waiting) {
return const Text("Loading");
}
if (snapshot.hasData) {
return SafeArea(
child: Center(
child: ListView(
children: snapshot.data!.docs
.map((DocumentSnapshot documentSnapshot) {
Map<String, dynamic> data =
documentSnapshot.data()! as Map<String, dynamic>;
return Container(
height: 200,
width: 100,
decoration: BoxDecoration(
image: DecorationImage(
image: NetworkImage('${data['ImgUrl']}'),
fit: BoxFit.contain,
),
),
);
}).toList(),
),
),
);
}
return const Text('Loading');
}),
);
}
}

Answer 1

You can't do that with this data structure. Firebase queries are shallow, meaning that you can't query a document together with the documents in sub collections.
In StreamBuilder you can get snapshots of either one specific document by setting :
FirebaseFirestore.instance
.collection(...)
.withConverter<...>(...)
.doc(...)
.snapshots()
or multiple documents:
FirebaseFirestore.instance
.collection(...)
.withConverter<...>(...)
.where(...)
.orderBy(...)
.limit(...)
.snapshots()
In both cases, you will get the data of one or more documents, but if you need the documents in a sub collection, you need to perform another query. For example if you have one document in doc variable, and you need data in its Today Photos sub collection, you need another stream:
doc.collection('Today Photos')
.withConverter<...>(...)
.snapshots()
So with the current data structure you can query into a StreamBuilder all documents in the user's photos collection, but the contents of Today Photos sub collection must be queried separately for each retrieved document of photos collection.
The other option is to change your data structure. You can add the daily photos to the photos collection, let Firebase assign an id to them and add the date as a field. This way you can have one stream for the photos, order them by date, add a limit etc.