Save nested objects in shared preferences - flutter

Question

I have an object that contains a json array , which am trying to store in shared preferences but i don't know how to do so .
This is my model :
import 'dart:convert';
import 'package:deepnrise/models/settings/perimeter.dart';
import 'package:deepnrise/models/user/user_perims.dart';
UserWithPerim user(String str) => UserWithPerim.fromJson(json.decode(str));
class UserWithPerim {
// ignore: non_constant_identifier_names
UserWithPerim({
required this.identifier,
required this.firstName,
required this.lastName,
required this.email,
required this.role,
required this.perimeters,
});
String identifier;
String firstName;
String lastName;
String email;
String role;
List<UserPerimeter> perimeters;
factory UserWithPerim.fromJson(Map<String, dynamic> json) {
return UserWithPerim(
identifier: json['identifier'] ?? "",
firstName: json['firstName'] ?? "",
lastName: json['lastName'] ?? "",
email: json['email'] ?? "",
role: json['role'] ?? "",
perimeters: (json['perimeters'] as List)
.map((p) => UserPerimeter.fromJson(p))
.toList(),
);
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
data['identifier'] = identifier;
data['firstName'] = firstName;
data['lastName'] = lastName;
data['role'] = role;
data['email'] = email;
data['perimeters'] = perimeters;
return data;
}
}
This the perimeters model :
import 'dart:convert';
Userperimeters(String str) => UserPerimeter.fromJson(json.decode(str));
String UserPerimToJson(UserPerimeter data) => json.encode(data.tojson());
class UserPerimeter {
// ignore: non_constant_identifier_names
UserPerimeter(
{required this.id, required this.label, required this.perimeterId});
// ignore: non_constant_identifier_names
int id;
String label;
int perimeterId;
factory UserPerimeter.fromJson(Map<String, dynamic> json) {
return UserPerimeter(
id: json['id'] ?? "",
label: json['label'] ?? "",
perimeterId: json["perimeterId"] ?? "");
}
Map<String, dynamic> tojson() => {
"id": id,
"label": label,
"perimeterId": perimeterId,
};
}
For now I've two models of my user object , one that contains the perils list and one that doesn't because whenever I try to store my user in shared prefs I get this exception thrown :
Unhandled Exception: type 'UserPerimeter' is not a subtype of type 'Map<String, dynamic>'
This is how am saving and reading my user:
saveUser(value) async {
final prefs = await SharedPreferences.getInstance();
String user = jsonEncode(User.fromJson(value));
prefs.setString(Preferences.USER_KEY, user);
}
Future<User?> getUser() async {
final prefs = await SharedPreferences.getInstance();
if (prefs.containsKey(Preferences.USER_KEY)) {
Map<String, dynamic> userMap =
jsonDecode(prefs.getString(Preferences.USER_KEY) ?? "");
User user = User.fromJson(userMap);
return user;
}
}
Is there a way with which I can store the whole user model with the perils object list without making two models of the user object ? thank you so much in advance.

Answer 1

The work around here to convert your whole json response to string.
save that string into sharedprefs, then you can call it back and decode it using:
var response = json.decode(prefs.getString("response");
So, the full idea:
prefs.setString("response",json.encode(response.body));
using that String as json format again:
MyModel model = MyModel.fromJson(json.decode(prefs.getString("response")));
I hope you find what you need from this idea.

Answer 2

Convert the list of perimeters to list of Json like this:
if (this.perimeters != null) {
data['perimeters'] = this.perimeters!.map((v) => v.toJson()).toList();
}