Firebase 快照到 json 颤振模型

Question

Hello i am trying to get data from a firebase database and save it in a model class exactly the same way as you do for http json so this is my class model

UsersModel usersModelFromJson(String str) => UsersModel.fromJson(json.decode(str));

class UsersModel {
    String age;
    String heigth;
    String userid;
    String username;
    String weigth;

    UsersModel({
        this.age,
        this.heigth,
        this.userid,
        this.username,
        this.weigth,
    });

    factory UsersModel.fromJson(Map<dynamic, dynamic> json) => UsersModel(
        age: json["age"],
        heigth: json["heigth"],
        userid: json["userid"],
        username: json["username"],
        weigth: json["weigth"],
    );

and this is how i try to get the data

Future obtenerDatos(userid) async {
  var bd = dB.child('users').child(userid).once().then((DataSnapshot snapshot) {
    Map<String, dynamic> values = snapshot.value;
    values.forEach((key, values) {

      return UsersModel.fromJson(values);
    });
  }

i get this error

`Unhandled Exception: type '_InternalLinkedHashMap<dynamic, dynamic>' is not a subtype of type 'Map<String, dynamic>'`

i have tried everything i can prit it as json but i dont understand why i cant save it to the model class i have 2 days with the same problem please help me

Answer 1

You have to change this line in obtenerDatos : Map<String, dynamic> values = snapshot.value;

To: Map<dynamic, dynamic> values = snapshot.value;

The error happens because your fromjson method expects map of the type <dynamic, dynamic> and you mapped the response like <String, dynamic>