Firestore increment int value if it is exist with flutter

Question

hi guys i am trying to develop an app but i need some help i have a function i just need to do if item is exist on firestore i need to increment "quantity" value of it. i already got and printing the value but i need some help for checker and incrementing value thanks

String checker = await Firestore.instance
        .collection('cart')
        .document('LIihBLtbfuJ8Dy640DPd')
        .get()
        .then((DocumentSnapshot ds) => ds.data[foodItem.name]);
    if (checker == foodItem.name) {
      await Firestore.instance
          .collection('cart')
          .document('LIihBLtbfuJ8Dy640DPd')
          .get()
          .then((DocumentSnapshot ds) =>
              a = ds.data[foodItem.name]['quantity']);

      Firestore.instance
          .collection("cart")
          .document("LIihBLtbfuJ8Dy640DPd")
          .updateData({
        foodItem.name: {'quantity': q++}
      });
    } else {
      Firestore.instance.runTransaction((Transaction transaction) async {
        await transaction.update(
            Firestore.instance
                .collection("cart")
                .document("LIihBLtbfuJ8Dy640DPd"),
            {
              foodItem.name: {
                'itemName': foodItem.name,
                'imgUrl': foodItem.imageAssetPath,
                'itemPrice': foodItem.price,
                'quantity': q,
              }
            });
      });
    }

this is picture of my firestore as you can see there is nested nodes there

Does this answer your question? [Firestore Increment FieldValue](https://stackoverflow.com/questions/54543067/firestore-increment-fieldvalue) — Shady Boshra, Apr 02 '20 at 01:45

wcyankees424 · Answer 1 · 2020-04-02T04:27:33.123

2

This is what you want to increment a value if the field doesn't exist firebase will create it with the value of 1. I am confused as to the checker part of your question.

Firestore.instance.collection("cart")
.document("LIihBLtbfuJ8Dy640DPd")
.setData({foodItem.name: {"quantity": FieldValue.increment(1)}});

edited Apr 02 '20 at 04:27

answered Apr 02 '20 at 01:23

wcyankees424

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Likely that needs to be: `updateData({ 'foodItem.name.quantity': FieldValue.increment(1) }).` – Frank van Puffelen Apr 02 '20 at 01:31
it does not work too because it is nested nodes by the way – Mehmet Reşat Demir Apr 02 '20 at 01:35
okay I copy and pasted your code ```FieldValue.increment(1)``` works I tried it in my app – wcyankees424 Apr 02 '20 at 01:39
it works but it is outside of the nodes creating new data – Mehmet Reşat Demir Apr 02 '20 at 02:12
it is not exactly changing my value it does not effect it – Mehmet Reşat Demir Apr 02 '20 at 02:13
I see whats happening it's because its nested its showing up on the same level as item right – wcyankees424 Apr 02 '20 at 02:25
as long as your code was writing to firebase correctly before you should be able to take your original code and just replace ```q++``` with ```FieldValue.increment(1)``` – wcyankees424 Apr 02 '20 at 02:31

Firestore increment int value if it is exist with flutter

1 Answers1