CODEWITHSUNDEEP
firebaseflutterdartgoogle-cloud-firestore
Rushwin Jamdas
Rushwin Jamdas

Reputation: 386

Can't figure out how to read data from Firestore document in a function

I am new to Flutter, and I'm trying to read and write data to a Firestore document when a QR code is scanned. I have been able to write data to my Firestore document, but I can't figure out the proper syntax to read data from the document. All the answers I've seen online use StreamBuilder to return values to a Text view, but I just need the values to use in my function, not show on the app screen.

Here's my code:

class _MyAppState extends State<MyApp> {
  String result="";

  Future _scanQR() async{
    String cameraScanResult = await scanner.scan();
    DateTime now = new DateTime.now();

    setState(() {
      result=cameraScanResult;
      
      DocumentReference document = FirebaseFirestore.instance
          .collection('coin_tracker')
          .doc(result);
      
      var num_of_uses = document.snapshots()['number_of_uses'];

      document.update({
        'checkout_date': Timestamp.fromDate(now),
        'number_of_uses': num_of_uses+1,
      });
    });

  }

The above worked fine to update the checkout_date based on the QR scan. But I can't figure out how to get the 'number_of_uses' value from the document to then add on to.

The document looks like this:

'1000000001' {
'checkout_date: October 4, 2020 at 4:43:22 PM UTC-6,
'number_of_uses':0,
}

Upvotes: 0

Views: 91

Answers (1)

Doug Stevenson
Doug Stevenson

Reputation: 317467

You probably just want to use get() for a one-time read that returns Future, as illustrated in the documentation.

DocumentReference reference = FirebaseFirestore.instance
    .collection('coin_tracker')
    .doc("the-doc-id");
DocumentSnapshot snapshot = await reference.get();
int number_of_uses = snapshot.get("number_of_uses");

Upvotes: 1

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