Develop Reference

Future is returning empty List

My below code is returning an empty list, even though it SHOULD return data corresponding to my data stored in my firestore database. Also to note: The otherUserId print statement is not getting printed. How can I fix this issue?
Future<List<String>> getChattingWith(String uid) async {
List<String> chattingWith = [];
try {
// create list of all users user is chatting with
final rooms = await FirebaseFirestore.instance
.collection('rooms')
.where('users', arrayContains: uid)
.get();
for (final room in rooms.docs) {
final users = room['users'] as Map<String, dynamic>;
final otherUserId = users['uid1'] == uid ? users['uid2'] : users['uid1'];
print("otherUserId999: $otherUserId");
chattingWith.add(otherUserId);
}
print("chattingWith: $chattingWith");
return chattingWith;
} catch (error) {
print("error: $error");
return [];
}
}

This part of your code does not match your data structure:
final rooms = await FirebaseFirestore.instance
.collection('rooms')
.where('users', arrayContains: uid)
.get();
Your users is a Map and not an array, so arrayContains won't work here. As said in my answer to your previous question, you have to use dot notation to test nested fields:
final rooms = await FirebaseFirestore.instance
.collection('rooms')
.where('users.uid1', isEqualTo: uid)
.where('users.uid2', isEqualTo: otherValue)
.get();
That 👆 is closest to what you tried in your previous question: Firestore conditional array query. It performs an AND condition on the uid1 and uid2 subfields of users.
If instead you want to get all rooms that the user is a participant in, you need an (additional) field that is an array with the UIDs of all participants.
participantUIDs: ["uid1", "uid2"]
Then you can do:
final rooms = await FirebaseFirestore.instance
.collection('rooms')
.where('participants', arrayContains: uid)
.get();

The return type 'List<dynamic>' isn't a 'FutureOr<List<Map<dynamic, dynamic>>>', as required by the closure's context Flutter

I wrote this code in older version of flutter, I think 1.8, but now I'm getting this error. How can I remove it. Here is the code -
getProviders(parentTicketId) async {
List<Map> orders = await _firestore
.collection('orders')
.where('parent_ticketId', isEqualTo: parentTicketId)
.get()
.then((value) => value.docs)
.then((value) =>
value.map((e) => {'id': e.id, ...e.data}).toList()); //This line is giving the error.
List<Map> providers = [];
for (var order in orders) {
providers.add(await _firestore
.collection('providers')
.doc(order['provider_id'])
.get()
.then((provider) => {
//TODO: Check
'name': provider.get('name'),
//'name': provider.data['name'],
'phone': provider.get('phone'),
//'phone': provider.data['phone'],
'order_ticketId': order['ticketId'],
'order_id': order['id'],
'id': provider.id,
}));
}

value.map((e) => {'id': e.id, ...e.data}).toList());
Here, you can not directly access id with e.id.
You should rather use e.data().id.
using fromJson or something similar like that is recommanded.

how to search through all documents for a specific field value

how to search through all documents for a specific field value
for eg: if i want the field: blood_group 'A+' from all documents and show me all documents which has 'A+' in it
https://i.stack.imgur.com/0IhT9.png
https://i.stack.imgur.com/4tkEG.png
source code

You can use the .where filter on the collection reference's query like below:
final QuerySnapshot querySnapshot = await FirebaseFirestore.instance.collection('users').where('blood_group', isEqualTo: 'A+').get();
final List<QueryDocumentSnapshot> documentSnapshotList = querySnapshot.docs;
for (QueryDocumentSnapshot snapshot in documentSnapshotList) {
print(snapshot.data());
}

You can use the .where option. Based on your firebase structure in the picture, you can use the following code, to get a list of all documents that satisfy your request.
Future<QuerySnapshot> bloodgroup (String bloodGroup) async {
return await FirebaseFirestore.instance.collection('Donation').where('blood_group', isEqualTo: bloodGroup).get();
}
void getDocs() async {
QuerySnapshot allResults = await bloodgroup('A+');
for (var item in allResults){
print(item.id); //this will print the id of all the documents which are A+.
}
}

Extracting info from QuerySnapshot variable in flutter app

This code is running fine with futurebuilder and i m getting a listview properly.
But i want to see into the documents n print the details in console. I m not getting any idea about how to do this with QuerySnapshot variable.
Future getP() async {
var firestore = Firestore.instance;
var q = await firestore.collection('place_list').getDocuments();
print(q.documents);
return q.documents;
}
I think I have to call it n wait for the responses then print them, can anyone guide me how to do it?

List<Map<String, dynamic>> list =
q.documents.map((DocumentSnapshot doc){
return doc.data;
}).toList();
print(list);

Though the answer is right the current firebase API has changed drastically now to access QuerySnapshot one can follow the below code.
FirebaseFirestore.instance
.collection('users')
.get()
.then((QuerySnapshot querySnapshot) => {
querySnapshot.docs.forEach((doc) {
print(doc["first_name"]);
});
});
And if you are using async/await then first you need to resolve the AsyncSnapshot and then work on it. If you like:
return FutureBuilder(
future: PropertyService(uid:userId).getUserProperties(),
builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot){
if (snapshot.hasError) {
return Text("Something went wrong");
}
if (snapshot.connectionState == ConnectionState.done) {
snapshot.data.docs.forEach((element) {
Property property = Property.fromJson(element.data());
});
return Text("Demo Text");
}
return LoadingPage();
}
);
taken from url

//But I am not getting all the documents present in my firestore DB collection. The first 10 or so entries are getting printed in the console. //
I think that is standard behavior. If you have one million records it can't print everything in console. To check any particular set of documents you have to filter through where condition in query.

If you have still this problem, I hope this will help you.
This is how I get data from QuerySnapshot:
QuerySnapshot snapshot =
await userCollection.where("uid", isEqualTo: uid).get();
List<Object?> data = snapshot.docs.map((e) {
return e.data();
}).toList();
Map<dynamic, dynamic> userData = data[0] as Map;
print(userData["email"]);
Or you can easily get data by:
QuerySnapshot querySnapshot =
await userCollection.where("uid", isEqualTo: uid).get();
print(querySnapshot.docs[0)['fieldName']);

Firestore - How create DocumentReference using path String

Firebase realtime database allowed to create refrence using
var reference = db.ref(path);
Is there any method exist in firestore so that I can create document refrence using path String.
If method exists how can I find path string in android and then how create document reference in node.js using that path.

Yes, you can achieve this also in Cloud Firestore. So these are your options:
FirebaseFirestore db = FirebaseFirestore.getInstance();
First option:
DocumentReference userRef = db.collection("company/users");
Second option:
DocumentReference userRef = db.document("company/users");
Third option:
DocumentReference userRef = db.collection("company").document("users");

For web/javascript, db.doc() will create a DocumentReference from a string:
let docRef = db.doc(pathString)
e.g. let userRef = db.doc('users/' + userId)

You can use FirebaseFirestore.document() and pass it the path of the document you want. Each document must be located within a collection. If you're looking for a document called documentId in a collection called collectionId, the path string will be collectionId/documentId.

you just need to define the path :
`users/${type}/${user.uid}/`
firestore
.collection(`users/${type}/${user.uid}/`)
.add(documentData)
.then(function () {
message = { message: "document added", type: ErrorType.success };
})
.catch(function (error) {
message = { message: error, type: ErrorType.error };
});

For Firestore web version 9 (after August 25, 2021) you can use doc() to generate a reference with an id:
import { collection, doc, setDoc, getFirestore } from "firebase/firestore";
// Add a new document with a generated id
const newRef = doc(collection(getFirestore(), "user"));
const data = {
id: newRef.id,
firstName: 'John',
lastName: 'Doe'
}
await setDoc(newRef, data);

Use "." instead of "/" for path
FirebaseFirestore db = FirebaseFirestore.getInstance();
db.collection(FBConstant.Product.Head)
.whereEqualTo("rating.$id", true)