Step 1 - toJson

class User {
  final String id;
  final String name;

  User({required this.id, required this.name});

  Map<String, dynamic> toJson() => {
        'id': id,
        'name': name,
      };
}

Step 2 - fromJson factory

class User {
  final String id;
  final String name;

  User({required this.id, required this.name});

  factory User.fromJson(Map<String, dynamic> json) {
    return User(
      id: json['id'] as String,
      name: json['name'] as String,
    );
  }

  Map<String, dynamic> toJson() => {
        'id': id,
        'name': name,
      };
}

void main() {
  final u = User.fromJson({'id': '1', 'name': 'Asha'});
  print(u.toJson());
}

Step 3 - Nested model

class Profile {
  final String bio;
  Profile(this.bio);

  factory Profile.fromJson(Map<String, dynamic> json) {
    return Profile(json['bio'] as String);
  }

  Map<String, dynamic> toJson() => {'bio': bio};
}

• User can hold a Profile and delegate toJson / fromJson for the nested object.

Practice tasks

• Add optional email (String?) and emit null or omit the key in toJson (pick one convention and stay consistent).
• Add List<Todo> on a User and serialize as a JSON array of objects.