Make a stream wait for data to assign a late property - flutter

Question

I have following code.
I need to assign a late userName (not stored in database BID table) from the Bid Object that i retreive from the firestore with a stream.
The userName can be found in another table in the database (USER table).
I need to connect those 2 all while a streambuilder is building with BID object stream coming in.
Repository
final _firestoreDB = FirebaseFirestore.instance;
Future<String> getDbUserNameFromDbUserID({required String dbUserID}) async {
try {
final docUser = _firestoreDB.collection('users').doc(dbUserID);
final snapshot = await docUser.get();
if (snapshot.exists) {
if (snapshot.data() != null){
return DbUser.fromJson(snapshot.data()!).userName;
}
}
throw Exception("getDBUserByDBUserId() No fireStore userName found");
} catch (e) {
throw Exception(e);
}
}
Stream<List<Bid>> getAllBidsByItemId({required String itemID}) {
try {
return _firestoreDB
.collection('bids')/*.orderBy('timestamp')*/
.where('itemID', isEqualTo: itemID)
.snapshots()
.map((snapshot) =>
snapshot.docs.map((doc) {
Bid bid = Bid.fromJson(doc.data());
bid.bidId = doc.id;
**bid.userName = await getDbUserNameFromDbUserID( dbUserID: bid.bidderID); ///????**
return bid;
}).toList());
} catch (e) {
throw Exception(e);
}
}
model
class Bid {
late String bidId;
**late String userName;**
final String bidderID;
final String itemID;
final double price;
final DateTime timestamp;
Bid(
{
required this.bidderID,
required this.itemID,
required this.price,
required this.timestamp});
Map<String, dynamic> toJson() => {
'bidderID': bidderID,
'itemID': itemID,
'price': price,
'timestamp': timestamp,
};
static Bid fromJson(Map<String, dynamic> json) => Bid(
bidderID: json['bidderID'],
itemID: json['itemID'],
price: json['price'],
timestamp: (json['timestamp'] as Timestamp).toDate(),
);
}
How can I assign the late String userName when the stream gets the objects from the firestore?
Whats the best practice to do this? I assume this is not the best way to go about it?
I am using Bloc and Firestore Firebase
Thank you
SOLUTION
Stream<List<Bid>> getAllBidsByItemId({required String itemID}) async* {
try {
yield* _firestoreDB
.collection('bids')
.where('itemID', isEqualTo: itemID)
.snapshots()
.asyncMap<List<Bid>>((event) async {
List<Bid> bids = [];
for (var doc in event.docs) {
try {
Bid bid = Bid.fromJson(doc.data());
bid.bidId = doc.id;
bid.userName = await getDbUserNameFromDbUserID( dbUserID: bid.bidderID);
bids.add(bid);
} catch (e) {
throw Exception(e);
}
}
return bids;
});
} catch (e) {
throw Exception(e);
}
}
This worked for me

Answer 1

SOLUTION
Stream<List<Bid>> getAllBidsByItemId({required String itemID}) async* {
try {
yield* _firestoreDB
.collection('bids')
.where('itemID', isEqualTo: itemID)
.snapshots()
.asyncMap<List<Bid>>((event) async {
List<Bid> bids = [];
for (var doc in event.docs) {
try {
Bid bid = Bid.fromJson(doc.data());
bid.bidId = doc.id;
bid.userName = await getDbUserNameFromDbUserID( dbUserID: bid.bidderID);
bids.add(bid);
} catch (e) {
throw Exception(e);
}
}
return bids;
});
} catch (e) {
throw Exception(e);
}}