How do I get rid of flutter data-table error using with StreamBuilder "Expected a value of type 'List<DataRow>', but got one of type 'List<dynamic>"?

Question

In code, code fetches data in a real-time(stream) manner from cloud firestore and shows it in the data-table widget using StreamBuilder, but when I run the code it gives the error as I asked above.

SizedBox(
     width: double.infinity,
     child: StreamBuilder(
           stream: FirebaseFirestore.instance.collection('products').snapshots(),
           builder: (BuildContext context,snapshot) {
           (!snapshot.hasData)? 
           Center(child: CircularProgressIndicator())
           : DataTable(
              // columnSpacing: defaultPadding,
              columns: [
                        DataColumn(label: Text("Id")),
                        DataColumn(label: Text("Name")),
                        DataColumn(label: Text("Category")),
                        DataColumn(label: Text("Image")),
                        DataColumn(label: Text("Original Price")),
                        DataColumn(label: Text("Sale Price")),
                        DataColumn(label: Text("Discount")),
                        DataColumn(label: Text("Commission")),
                        DataColumn(label: Text("Date")),
                       ],
              rows: _listofRows(snapshot.data),
        );
  })),

_listofRows method code here

List<DataRow> _listofRows(snapshot) {
  List<DataRow> newList = snapshot.docs.map((docSnapshot) {
    return  DataRow(cells: <DataCell>[
     DataCell(Text(docSnapshot.data()['ProductID'].toString())),
     DataCell(Text(docSnapshot.data()['Product Name'].toString())),
     DataCell(Text(docSnapshot.data()['Category Name'].toString())),
     DataCell(Text(docSnapshot.data()['Product ImageUrl'].toString())),
     DataCell(Text(docSnapshot.data()['originalPrice'].toString())),
     DataCell(Text(docSnapshot.data()['salePrice'].toString())),
     DataCell(Text(docSnapshot.data()['Discount'].toString())),
     DataCell(Text(docSnapshot.data()['Commission Rate'].toString())),
     DataCell(Text(doctSnapshot.data()['Out of Stock Date'].toString())),
    ]);
  }).toList();

  return newList;
}

this is one of the document examples of products collection on firestore database. (link of product document)

Majid Ali Khan · Accepted Answer · 2021-09-02 21:22:20Z

The solution is to provide a type argument to the map method.

List<DataRow> _listofRows(snapshot) {
  List<DataRow> newList = snapshot.docs.map<DataRow>((docSnapshot) {
    return  DataRow(cells: <DataCell>[
     DataCell(Text(docSnapshot.data()['ProductID'].toString())),
     DataCell(Text(docSnapshot.data()['Product Name'].toString())),
     DataCell(Text(docSnapshot.data()['Category Name'].toString())),
     DataCell(Text(docSnapshot.data()['Product ImageUrl'].toString())),
     DataCell(Text(docSnapshot.data()['originalPrice'].toString())),
     DataCell(Text(docSnapshot.data()['salePrice'].toString())),
     DataCell(Text(docSnapshot.data()['Discount'].toString())),
     DataCell(Text(docSnapshot.data()['Commission Rate'].toString())),
     DataCell(Text(doctSnapshot.data()['Out of Stock Date'].toString())),
    ]);
  }).toList();

  return newList;
}

If you want to check more, there is a similar answer of type inference fails in an unexpected way.

[Thanks @Jonah Williams] : https://stackoverflow.com/users/4231909/jonah-williams

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