Flutter Firestore: Building my model from a snapshot - firebase

Question

I'm struggling to build my model from firestore map. It seems basic yet I can't figure it out.
Here's my code :
firestore_service.dart
{
// ...
final FirebaseFirestore _db = FirebaseFirestore.instance;
await _db
.collection('Users')
.doc('jWtp19r7g2b4wwMJ5yBi')
.get()
.then((snapshot) {
print(snapshot);
print(snapshot.runtimeType);
final _data = snapshot.data() ?? {};
print(_data);
print(_data['uid']);
final user = UserModel.fromJson(_data);
print(user.uid);
return user;
});
}
user_model.dart
import 'package:flutter/material.dart';
class UserModel {
// ...
factory UserModel.fromJson(Map<String, dynamic> json) {
return UserModel(
uid: json['uid'],
username: json['username'],
characterID: json['character_id'],
);
}
}
Terminal
Can anyone help me?

Answer 1

Okay so, I don't know if it's a "clean" way of doing it but I figured I could add another factory in my model to build specifically from Firestore.
Since the specific error was Unhandled Exception: type 'List<dynamic>' is not a subtype of type 'List<String>', I duckduckgo-ed the error and found this solution :
service.dart
await _db
.collection('Users')
.doc('jWtp19r7g2b4wwMJ5yBi')
.get()
.then((snapshot) {
final _data = Map<String, dynamic>.from(snapshot.data() ?? {});
print(_data.runtimeType);
final user = UserModel.fromFirestore(_data);
print(user.uid);
});
user_model.dart
class UserModel {
UserModel({
required this.uid,
required this.characterID,
this.username,
});
final String uid;
final String? username;
final List<String> characterID;
factory UserModel.fromJson(Map<String, dynamic> json) {
return UserModel(
uid: json['uid'],
username: json['username'],
characterID: json['character_id'],
);
}
factory UserModel.fromFirestore(Map<dynamic, dynamic> json) {
return UserModel(
uid: json['uid'],
username: json['username'],
characterID: List<String>.from(json['character_id']),
);
}
Map<String, dynamic> toJson() => {
"uid": uid,
"username": username,
"character_id": characterID,
};
}
I feel like it's not my factory's role to "filter / cast" the data but that's the only way I found it working.