Flutter: Undefined name Try correcting the name to one that is defined, or defining the name - flutter

Question

I am facing a few strange issues with Flutter. I do have very little knowledge about Flutter. I am learning it.
class ViewOtherProfile extends StatefulWidget {
final String userName;
final int points;
const ViewOtherProfile({
#required this.userName,
#required this.points,
});
You can see i am getting userName and Points data as argument.
I want to print this argument in the page. Like this
class _ViewOtherProfileState extends State<ViewOtherProfile> {
..........
void initState(){
print(points);
deviceInfo();
super.initState();
print(userName);
]);
}
............
Now problem is i am getting error.
Undefined name 'userName'.
Try correcting the name to one that is defined, or defining the name.
Any reason why i am getting this error and how i can resolve it.
Thanks to #jamesdlin
I tried to put it like this
print(ViewOtherProfile.userName);
but now i am getting another error.
Instance member 'userName' can't be accessed using static access.

Answer 1

There are two main types of widgets in Flutter. StatelessWidget and StatefullWidget. A StatelessWidget is built only one when the UI builds and is never rebuilt. Meanwhile, a StatefulWidget can be rebuilt every time if a call for setState is made.
Hence, for a StatefulWiget, there is a need to track the state of the class by extending the main class with a State class.
You have to note that the scope of variables in those two types of widgets can vary. For example...
class ExampleStateless extends StatelessWidget {
final String userName;
final int points;
const ExampleStateless({
#required this.userName,
#required this.points,
});
#override
Widget build(BuildContext context){
print(userName); print(points);
return Something();
}
}
Note that for the stateful widget, there are two classes and each class has its scope. The superclass ExampleStateful can share its scope to its subclass _ExampleStatefulState via the widget
class ExampleStateful extends StatefulWidget {
final String userName;
final int points;
Static final string id = "exampleState";
const ExampleStatefull({
#required this.userName,
#required this.points,
});
// scope 1
#override
_ExampleStatefulState createState() => _ExampleStatefulState();
}
class _ExampleStatefulState extends State<ExampleStateful>{
// scope 2
final String userName2 = null;
#override
void initState(){
super.initState();
print(widget.userName);
print(userName2);
print(ExampleStateful.id); // you can do this only if variable is static.
}
}
What is in scope 1 can be accessed in scope 2 via the widget properties. eg print(widget.userName); instead of print(userName);