Dart extension type

main.dart

/*
 * Extension type
 * https://gist.github.com/PlugFox/5593eafa163371223c7c2068266cc1b7
 * https://dartpad.dev?id=5593eafa163371223c7c2068266cc1b7
 * Mike Matiunin <plugfox@gmail.com>, 30 January 2026
 */

import 'dart:convert';

void main() {
  print(const SignInMeta.empty());
  print(jsonEncode(SignInMeta(uiFlowSource: 'source')));
}

extension type const SignInMeta._(Map<String, Object?> _map)
    implements Map<String, Object?> {

  const SignInMeta.empty() : _map = const {};

  factory SignInMeta({
    String? uiFlowSource,
    bool? isSignUp,
  }) => SignInMeta._({
      'is_sign_up': isSignUp ?? false,
      'ui_flow_source': ?uiFlowSource,
  });

  String? get uiFlowSource => _map['ui_flow_source']?.toString();

  bool get isSignUp => _map['isSignUp'] == true;

  Map<String, Object?> toMap() => <String, Object?>{...this};
}