I'm trying to list a realtime database. I have the problem that the way of data are mapped, but i'm not understand how to solve.

My code is:

Future<List<ProductoLeido>> getProductosEnGia() async {
  List<ProductoLeido> prdEnGia = [];

  try {
    DatabaseEvent event =
        await FirebaseDatabase.instance.ref().child('ProductosEnGIA').once();

    if (event.snapshot.exists) {
      DataSnapshot s = event.snapshot;
      print("out forEach");
      Map<String, Object?>.from(s.value as dynamic).forEach((key, value) => {
            print('key:'   key),
            print("in forEach"),
          });
    }

    return prdEnGia;

  } catch (e) {

    return prdEnGia;

  }
}

And the returned is:

TypeErrorImpl (Expected a value of type 'Map<dynamic, dynamic>', but got one of type 'List')

I'm attach image to share more data in debug mode.

CodePudding user response：

I made a output of snapshot value, and the results is:

Output

CodePudding user response：

It looks like the data you're reading has sequential, numeric keys, which means that the Firebase SDK maps it to an array/list and not to a map.

So instead of:

Map<String, Object?>.from(s.value as dynamic)

You'll want to use:

List<Object?>.from(s.value as dynamic)

I recommend reading this blog post to learn more about how Firebase handles arrays: Best Practices: Arrays in Firebase.

CodePudding user response：

Done. I solve the problem. That is the solution:

 Future<List<ProductoLeido>> getProductosEnGia() async {
List<ProductoLeido> prdEnGia = [];

try {
  DatabaseEvent event =
      await FirebaseDatabase.instance.ref().child('ProductosEnGIA').once();

  if (event.snapshot.exists) {
    DataSnapshot s = event.snapshot;
    final m = s.value as List<dynamic>;
    for (int i = 0; i < m.length; i  ) {
      final p = ProductoLeido.fromJson(m[i]);
      print(m[i].toString());
      Map<dynamic, dynamic> d = m[i];
      ProductoLeido.fromJson(d);
      var cod = ProductoLeido.fromJson(d).codigo;
      var cant = ProductoLeido.fromJson(d).cantidad;
      print('CODIGO>>>>'   cod.toString());
      ProductoLeido prL = ProductoLeido(cod, cant);
      prdEnGia.add(prL);
    }
  }

  return prdEnGia;
} catch (e) {
  return prdEnGia;
}

}