Save a List to SharedPreferences - flutter

Question

I am trying to save the list dragged from the sql to be saved in SharedPreferences, I tried using this code:
static Future<List<User>> getUsers() async {
final myUserId = await getUser();
try {
var myUser = myUserId;
var map = Map<String, dynamic>();
map['user'] = myUser;
final response = await http.post(ROOT, body: map);
//print('getUsers Response: ${response.body}');
//print(myUser);
if (200 == response.statusCode) {
List<User> listContacts = parseResponse(response.body);
SharedPreferences contacts = await SharedPreferences.getInstance();
contacts.setStringList('contacts', listContacts);
return listContacts;
} else {
return List<User>();
}
} catch (e) {
return List<User>(); // return an empty list on exception/error
}
}
the User class for the list is the following:
class User {
final String firstName;
final String lastName;
final String imageLink;
User({this.firstName, this.lastName, this.imageLink});
factory User.fromJson(Map<String, dynamic> json) {
return User(
firstName: json['firstName'] as String,
lastName: json['lastName'] as String,
imageLink: json['imageLink'] as String,
);
}
}
So basically the data is successfully pulling it out from the database, and it does display it, but I want to save the data to SharedPreferences so it doesn't have to load every single time. The error that is occurring is that the listContacts can't be assigned to setStringList, since it is a List<User> and not a List<String>, but I don't know how else can I change the code in order to be able to set the SharedPreferences.

Answer 1

Here you can do is
static Future<List<User>> getUsers() async {
final myUserId = await getUser();
try {
var myUser = myUserId;
var map = Map<String, dynamic>();
map['user'] = myUser;
final response = await http.post(ROOT, body: map);
//print('getUsers Response: ${response.body}');
//print(myUser);
if (200 == response.statusCode) {
List<User> listContacts = parseResponse(response.body);
SharedPreferences contacts = await SharedPreferences.getInstance();
contacts.setString('contacts',json.encode(response.body)); //Here saved the response
return listContacts;
} else {
return List<User>();
}
} catch (e) {
return List<User>(); // return an empty list on exception/error
}
}
Now to fetch it I can use is
SharedPreferences contacts = await SharedPreferences.getInstance();
var response = json.decode(contacts.getString('contacts'));
List<User> listContacts = parseResponse(response.body);
and you get back your data from shared preferences