如何在 Flutter 中创建新用户后将默认用户名、主题模式和主题颜色存储到 Cloud Firestore？

Question

When a new user is created in Firebase, I want to create a collection of user preferences and save it to Cloud Firestore as well. All defaulted to username String 'John Doe', thememode ThemeMode.light and themecolor FlexScheme.money (using flexcolorscheme package).

I can store Strings and int's (works fine with my code), but not ThemeModes apparently and I don't know how to solve this correctly.

I created a PrefService class:

class PrefService {
  //Declare a nullable String to hold user unique ID
  final String? uid;

  //When we call PrefService, require to insert user unique ID
  PrefService({this.uid});

  final CollectionReference<Object?> userPreferences =
      FirebaseFirestore.instance.collection('userPreferences');

  Future<dynamic> updateUserPreferences(
    String name,
    ThemeMode themeMode,
    FlexScheme themeColor,
  ) async {
    //If document doesn't exist yet in Firebase, it will be created under user unique ID
    return userPreferences.doc(uid).set(<String, dynamic>{
      'name': name,
      'themeMode': themeMode,
      'themeColor': themeColor,
    });
  }
}

And an AuthService class:

class AuthService {
  //Sign UP user only with email and password
  Future<void> signUp({
    required String email,
    required String password,
    required BuildContext context,
  }) async {
    await FirebaseAuth.instance.createUserWithEmailAndPassword(
      email: email,
      password: password,
    );
    //After creating a user, create a database file under user unique ID as well
    //Store default name, themeMode and themeColor, which can be adjusted later by user.
    Logger().i('Database record created for user');
    await PrefService(uid: FirebaseAuth.instance.currentUser!.uid)
        .updateUserPreferences(
      'John Doe',
      ThemeMode.light,
      FlexScheme.money,
    );
etc...

When I set all parameters of updateUserPreferences() to type String, everything works and I get a nice collection under a unique user ID. But it does not let me store parameter of type ThemeMode:

[ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: Invalid argument: Instance of 'ThemeMode'

Why can I store a String, but not a ThemeMode? I want users to be able to change these settings in a SettingsScreen(), but how should I store them correctly?

I am aware of the existence of SharedPreferences, but I want to do it this way. If anyone can show me how (and why) I should handle this, it would be greatly appreciated.

Answer 1

Objects cannot be saved in firebase directly. If it is Model you can store it in map format. In your case shore the them mode as String or int ie 0 for light and 1 for dark and convert it when you read the data.