Flutter Firestore error adding value to value from Firestore

I’ve got an error while i tried to add value to value from firestore.
I want to sum value from kcal variable with firestore "progress" value

progressAdd = nutr + kcal2;

Error screenshot

Future addMeal() async {
    var nutr;
    await FirebaseFirestore.instance
        .collection('usersData')
        .doc(FirebaseAuth.instance.currentUser!.uid)
        .get()
        .then((doc) => {nutr = doc.data()});
    print('test');
    if (nutr != null) {
      this.progress = nutr['progress'];
      setState(() {
        progressAdd = nutr + kcal2;
        FirebaseFirestore.instance
            .collection('usersData')
            .doc(FirebaseAuth.instance.currentUser!.uid)
            .update({'progress': progressAdd});
      });
    } else {
      print('test2');
      return showDialog(
          context: context,
          builder: (context) {
            return AlertDialog(
              backgroundColor: mainFontColor().tsubColor,
              title: Text(
                ':/',
                textAlign: TextAlign.center,
                style: GoogleFonts.lato(
                    fontWeight: FontWeight.w600, color: Colors.white),
              ),
              content: Container(
                height: 120,
                width: 250,
                child: Column(children: [
                  Text(
                    'Something went wrong!',
                    style: GoogleFonts.dosis(color: Colors.white),
                  ),
                  SizedBox(
                    height: 5,
                  ),
                  Text(
                    'Go back and try again!',
                    style: GoogleFonts.dosis(color: Colors.white),
                  ),
                  SizedBox(
                    height: 20,
                  ),
                  Container(
                    height: 40,
                    width: 180,
                    child: ElevatedButton(
                        child: Text('OK'),
                        style: ElevatedButton.styleFrom(
                            backgroundColor: mainFontColor().tsubColor2),
                        onPressed: (() => Navigator.pop(context))),
                  )
                ]),
              ),
            );
          });
    }
  }

>Solution :

This line:
.then((doc) => {nutr = doc.data()});

will assign the doc.data() which have a type of Map<String, dynamic> to the nutr variable.

so, this:

 progressAdd = nutr + kcal2;

is actually not valid, because you want to make an addition over objects that can’t be summed, nutr have a type of Map<String, dynamic> and kcal2 is double.

from the code I read, I assume that you want to get the existing progress on the Firestore document and update it with the sum of it + kcal2, so try the following:

instead of:

progressAdd = nutr + kcal2;

replace with this:

progressAdd = this.progress + kcal2;

this now should be valid that you want to sum to numbers the update in Firestore.