Casting an Object as a Map when Firebase RTDB is updated

Question

I'm doing a query in Firebase RTDB as follows:

Future<UsuarioModel> cargarUsuarioEmpresa(String idEmpresa, String idUsuario) async {

  UsuarioModel _usuario = UsuarioModel();     
  Query resp = db.child('PATH/usuarios/$idUsuario');  
  final snapshot = await resp.once(); 
  _usuario = UsuarioModel.fromJson(Map<String, dynamic>.from(snapshot.value));
  return _usuario;

} 

It was working perfect until I upgraded firebase_database package from 8.0.1 to 9.0.3

Now, I have an error

The getter 'value' isn't defined for the type 'DatabaseEvent'.

Then, I updated my method to receive a DatabaseEvent:

  final event = await resp.once();
  _usuario = UsuarioModel.fromJson(Map<String, dynamic>.from(event.snapshot.value));

But an error appears:

The argument type 'Object?' can't be assigned to the parameter type 'Map<dynamic, dynamic>'.

I tried to add an as casting:

  _usuario = UsuarioModel.fromJson(Map<String, dynamic>.from(event.snapshot.value as Map<String,dynamic>));

but It doesn't work. I get an error after build:

Unhandled Exception: type '_InternalLinkedHashMap<Object?, Object?>' is not a subtype of type 'Map<String, dynamic>' in type cast

How can I cast properly a Map of Objects as a Map<String, dynamic> to fix the error?

Answer 1

Due to changes in version 9 from dynamic to object, you can define the snapshot value as dynamic:

      final event = await resp.once();
      _usuario = UsuarioModel.fromJson(Map<String, dynamic>.from(event.snapshot.value as dynamic));

It's a workaround, but it does work!