Store documents from firestore in list - firebase

Question

I am trying to retrieve documents from collection called "Org" and store it in list to display in the dropdownmenu, but the list returns [Instance of 'QueryDocumentSnapshot', Instance of 'QueryDocumentSnapshot'] and thus i get following error:
The method 'map' was called on null.
Receiver: null
Tried calling: map(Closure: (dynamic) => DropdownMenuItem<dynamic>)
This is the code i implemented:
void organisation() async {
await Firebase.initializeApp();
QuerySnapshot querySnapshot = await FirebaseFirestore.instance.collection("Org").get();
final List<DocumentSnapshot> list = querySnapshot.docs;
print(list);
list.forEach((data) => print(data));
}
#override
initState() {
Firebase.initializeApp();
organisation();
super.initState();
}
This is how i implemented dropdownmenu:
DropdownButtonFormField(
validator: (value) => value == "Select" ? 'Field required' : null,
value: _selectorg,
onChanged: (val) => setState(() => _selectorg = val),
items: list.map(
(item) {
return DropdownMenuItem(
child: Text('$item'),
value: item,
);
},
).toList(),
hint: Text(
"SELECT ORGANISATION",
style: TextStyle(color: Colors.white)),
),

Answer 1

Try this,
#override
initState() {
super.initState();
Firebase.initializeApp();
organisation();
}
And,
Declare your list outside the function
final List<DocumentSnapshot> list;
void organisation() async {
await Firebase.initializeApp();
QuerySnapshot querySnapshot = await FirebaseFirestore.instance.collection("Org").get();
list = querySnapshot.docs;
print(list);
list.forEach((data) => print(data));
}
Update
StreamBuilder(
stream: FirebaseFirestore.instance.collection("Org").get();
builder: (BuildContext context,
AsyncSnapshot<QuerySnapshot> snapshots) {
if (snapshots.connectionState == ConnectionState.active &&
snapshots.hasData) {
print(snapshots.data);
return ListView.builder(
itemCount: snapshots.docs.length,
itemBuilder: (BuildContext context, int index) {
DocumentSnapshot doc = snapshots.data[index];
Map data= doc.data;//This is your data
return Text(
data.toString(),
);
},
);
} else {
return Center(child: CircularProgressIndicator());
}
},
),