Instance_id.dart

import 'package:shared_preferences/shared_preferences.dart';
import 'package:uuid/uuid.dart';

class InstanceId {
  InstanceId._();

  factory InstanceId() => _instance ?? (_instance = InstanceId._());

  static InstanceId? _instance;

  static const String _key = 'InstanceId';
  String? _value;

  Future<String> get() async {
    if (_value != null) {
      return _value!;
    }
    final prefs = await SharedPreferences.getInstance();
    String storedId = prefs.getString(_key) ?? '';
    if (storedId.trim().isEmpty) {
      storedId = const Uuid().v1();
      await prefs.setString(_key, storedId);
    }
    return _value = storedId;
  }

  Future<void> dispose() async {
    final prefs = await SharedPreferences.getInstance();
    await prefs.remove(_key);
    _value = null;
  }
}