FLUTTER and FIREBASE: How to increment an int in a map?

Question

I use flutter + firebase and I have a problem, in my db I have a 'Votes' value that is an array of 2 int. I want to increment them using like this : 'Votes': [FieldValue.increment(nb1), FieldValue.increment(nb2)], but it is not working, so I'm stuck I don't know how to increment them.

  Future vote(String voteid) async {
    List<dynamic> listvote = [];
    List<dynamic> vote1 = [];
    List<dynamic> vote2 = [];
    List<dynamic> votevierge = [];
    var vote = nomines.indexOf(voteid);
    int nb1 = 0;
    int nb2 = 0;

    final snapShot =
        await Firestore.instance.collection('rooms').document(pincode).get();
    if (snapShot != null) {
      listvote = snapShot.data['Votes'];
      vote1 = snapShot.data['Vote1'];
      vote2 = snapShot.data['Vote2'];
      listvote[vote] = listvote[vote] + 1;
      if (vote == 0) {
        votevierge = List.from(vote1);
        votevierge.add(nameid);
        nb1 = 1;
      } else {
        votevierge = List.from(vote2);
        votevierge.add(nameid);
        nb2 = 1;
      }
      vote++;
      Firestore.instance.collection('rooms').document(pincode).updateData({
        'Votes': [FieldValue.increment(nb1), FieldValue.increment(nb2)],
        'Vote$vote': votevierge,
      });
    }
  }

Answer 1

You can increment the value of a field by .set() method with Setoptions().

For example, i have a map of question in the firebaseFirestore and i want to increment the value of 'upVotes' key by 1 then :

.

 FirebaseFirestore.instance.collection('questions').doc(questionId).set({

 'question' : {
 'upVotes' : FieldValue.increment(1),
 },
 // This option helps in merging with initial  data

 SetOptions(merge:true),

 });