The named parameter 'semesters' is required, but there's no corresponding argument-CodePudding

main.dart `

void main() {
  runApp(
    Provider(
      create: (_) => LoginService(),
      child: MaterialApp(
        theme: ThemeData(fontFamily: 'Roboto'),
        debugShowCheckedModeBanner: false,
        routes: {
          '/': (context) => SplashPage(goToPage: WelcomePage(), duration: 3),
          '/welcomepage' : (context) => WelcomePage(),
          '/categorylistpage' : (context) => CategoryListPage(),
          '/selectedcategorypage' : (context) => SelectedCategoryPage(),
        }
      ),
    )
  );
}

selectedcategorypage.dart `

class SelectedCategoryPage extends StatelessWidget {
  final MyCategory? selectedCategory;
  final List<MySemester> semesters;
  const SelectedCategoryPage({
    Key? key,
    this.selectedCategory,
    required this.semesters,
  }) : super(key: key);

I tried to make the routs but for selectedcategory I have required this.semesters which I don't need a required to but without it I get this error: The parameter 'semesters' can't have a value of 'null' because of its type, but the implicit default value is 'null'. I don't know how to get around it

CodePudding user response：

You can provide a default value for the semesters parameter so that it is not required. You can do this by using the = operator after the parameter type and providing a default value, like this:

class SelectedCategoryPage extends StatelessWidget {
  final MyCategory? selectedCategory;
  final List<MySemester> semesters = [];
  const SelectedCategoryPage({
    Key? key,
    this.selectedCategory,
    required this.semesters,
  }) : super(key: key);
}

Now, if the semesters parameter is not provided, it will default to an empty list. You can also use a default value of null if you want to allow the value to be null and handle that case in your code.

CodePudding user response：

If the parameter 'semesters' is not required, then just remove the 'required' tag and make the variable nullable. Like:

 final List<MySemester>? semesters;

Full code:

class SelectedCategoryPage extends StatelessWidget {
  final MyCategory? selectedCategory;
  final List<MySemester>? semesters;
  const SelectedCategoryPage({
    Key? key,
    this.selectedCategory,
    this.semesters,
  }) : super(key: key);