Class

void main(){
    final erik = User(nickname: 'Amogus', age: 3, height:3.47);
    print(erik.nickname);
    print(erik.age);
    print(erik.height);
}

class User{
    User({required this.nickname, required this.age, this.height=2});
    final String nickname;
    final int age;
    final double height;
}