getting a specific field from every document in a collection

Question

I am using Dart Flutter and Firebase Firestore. I have a collection order with auto-ID'd documents containing a name and price. I want to set a double total to a sum of every price in the collection 'order'.

I have set up a query snapshot, forEach function, and docs.get() method. I have tried to set up as a map, and consulted chatGPT. The total isn't either updating or getting the price of each doc. I have used an initState() { calculateTotal(); } to call the function.

  double total = 0;

  Future<void> calculateTotal() async {
    total = 0;

    QuerySnapshot querySnapshot =
        await FirebaseFirestore.instance.collection('order').get();

    querySnapshot.docs.forEach((doc) {
      total += doc.get('price');
    });
  }

  @override
  Widget build(BuildContext context) {
    
    initState() {
      calculateTotal();
    }

Answer 1

QuerySnapshot<Map<String, dynamic>> querySnapshot =
await FirebaseFirestore.instance.collection('order').get();

querySnapshot.docs.forEach((doc) {
 total += double.tryParse(doc['price']??"0")??0;
});

you can try this code snipped