How do I add items of multiple arrays with respect to their indexes in dart?

Question

CODE:

  void func({String value}) async {
   
      final QuerySnapshot snapshot = await _firestore
          .collection('users')
          .where("id", isEqualTo: signedInUser.id)
          .get();

      snapshot.docs.forEach((element) {
        List<dynamic> arr = element.data()["array"];

        print(arr);

        }
}

OUTPUT:

I/flutter (27759): [10, 20, 30, 33, 34, 24]
I/flutter (27759): [2, 42, 45, 23, 85, 51]
I/flutter (27759): [32, 53, 12, 67, 34, 23]

This is what I get when I print the list from Firebase document.

How do I add items of the arrays for each respective indexes? Like; 10 + 2 + 32 for index 0

Answer 1

You should be able to get the List of Lists and then using a for loop sum the data like:

var lists = snapshot.docs.map((e) => e.data()['array']);
var sums = <int>[];
for (int i = 0; i < lists.first.length; i++) {
  var sum = 0;
  for (var list in lists) {
     sum += list[i];
  }
  sums.add(sum);
}

Be aware that this code is not tested, and you need to make sure that the lists are of equal length or the code might not work as you expect/throw an exception.