Getting One-Time Read Data From Nested Firestore in Flutter - firebase

Question

I'm currently trying to make an app that need to read data just for one time from a nested Firestore Database.
Here's my currently working code
FirebaseFirestore firestore = FirebaseFirestore.instance;
CollectionReference users = firestore.collection('users');
FirebaseAuth _auth = FirebaseAuth.instance;
FutureBuilder getTheData = FutureBuilder<DocumentSnapshot>(
future: users.doc(_auth.currentUser!.uid).get(),
builder:
(BuildContext context, AsyncSnapshot<DocumentSnapshot> snapshot) {
if (snapshot.hasError || (snapshot.hasData && !snapshot.data!.exists)) {
return Text("Something went wrong");
}
if (snapshot.connectionState == ConnectionState.done) {
Map<String, dynamic> data =
snapshot.data!.data() as Map<String, dynamic>;
String _condition = data['condition'];
String _descCondition = data['descCondition'];
int _percentageValue = data['percentageValue'];
return defaultDraw(
condition: _condition,
descCondition: _descCondition,
percentageValue: _percentageValue,
);
}
return defaultDraw(
condition: "Loading",
descCondition: "",
percentageValue: 0,
);
},
);
and it's able to read this data (condition, descCondition, and percentageValue) :
but when I'm trying to read this data :
Which is another collection inside of the previous document (a collection named 'adviceData' with random document ID that I'm trying to read), I'm getting an error like this :
Here's my code :
FirebaseFirestore firestore = FirebaseFirestore.instance;
CollectionReference users = firestore.collection('users');
FirebaseAuth _auth = FirebaseAuth.instance;
FutureBuilder _getParameterData = FutureBuilder<DocumentSnapshot>(
future: users
.doc(_auth.currentUser!.uid)
.collection('adviceData')
.doc()
.get(),
builder:
(BuildContext context, AsyncSnapshot<DocumentSnapshot> snapshot) {
if (snapshot.hasError || (snapshot.hasData && !snapshot.data!.exists)) {
return Text("Something went wrong");
}
if (snapshot.connectionState == ConnectionState.done) {
Map<String, dynamic> data =
snapshot.data!.data() as Map<String, dynamic>;
String _advicePhLow = data['advicePhLow'];
String _advicePhHigh = data['advicePhHigh'];
String _adviceTempLow = data['adviceTempLow'];
String _adviceTempHigh = data['adviceTempHigh'];
String _adviceHeightLow = data['adviceHeightLow'];
String _adviceHeightHigh = data['adviceHeightHigh'];
return drawParameter(
advicePhLow: _advicePhLow,
adviceTempLow: _adviceTempLow,
adviceHeightLow: _adviceHeightLow,
);
}
return drawParameter();
},
);
and my question is :
Where did I make mistakes?
Is there any better method to get a data from firestore?
Thanks in advance

Answer 1

If you want to get all documents from the subcollection adviceData you would need to get a QuerySnapshot like here:
FutureBuilder<QuerySnapshot>(
future: users
.doc(_auth.currentUser!.uid)
.collection('adviceData')
.get(),
builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
if (snapshot.hasError) {
return Text('Something went wrong');
}
if (snapshot.connectionState == ConnectionState.waiting) {
return Text("Loading");
}
return ListView(
children: snapshot.data!.docs.map((DocumentSnapshot document) {
Map<String, dynamic> data = document.data()! as Map<String, dynamic>;
return ListTile(
title: Text(data['full_name']),
subtitle: Text(data['company']),
);
}).toList(),
);
},
);
}
If you want to get a single document from that subcollection you would need to define the id of that specific document:
FutureBuilder _getParameterData = FutureBuilder<DocumentSnapshot>(
future: users
.doc(_auth.currentUser!.uid)
.collection('adviceData')
.doc('documentID') // here
.get(),
builder:
You can find more about both methods here.