Dart/Flutter widget with optional parameters but at least one required - flutter

Question

I'm trying to create a Flutter widget that can be initialized by various parameters, something like this
class MyWidget extends StatefulWidget {
final int? id;
final String? username;
MyWidget({this.id, this.username});
#override
_MyWidgetState createState() => _MyWidgetState();
}
class _MyWidgetState extends State<MyWidget> {
#override
void initState() {
super.initState();
if (widget.id != null) {
// init based on id
} else if (widget.username != null) {
// init based on username
} else {
// this should never happen
}
}
#override
Widget build(BuildContext context) {
return Container(); // build some widget
}
}
As you can see, neither of id and username are required, but I would need that at least one of them present. What would be a good way to approach this?

Answer 1

You can declare the constructor as anyone of these
MyWidget(this.id,{this.username});//ID is required. Usage will be MyWidget(1,usename:'test');
MyWidget(this.username,{this.id});//username is required Usage will be MyWidget('test',id:1);
MyWidget({required this.id, this.username}); //id required
MyWidget({this.id, required this.username});//username required
MyWidget({requried this.id, required this.username});//both required
And you can also use Assert Statement to check values at runtime have a look
MyWidget({this.id, this.username}):assert(id != null && username != null,'Both parameters cannot be null');

Answer 2

class TestWidget extends StatelessWidget {
final String id;
final String name;
const TestWidget.name({this.id, #required this.name});
const TestWidget.id({#required this.id, this.name});
#override
Widget build(BuildContext context) {
return Container(
child: Text(id ?? name),
);
}
}