How to initialize Either Right to an empty value in flutter

How do I correctly initialize my Either object in the following code?

class JobListState extends Equatable {
  const JobListState({
    this.status = JobListStatus.initial,
    this.jobListSections = Right([]),
    this.filter,
  });

  final JobListStatus status;
  final Either<Failure, List<JobListViewmodel?>> jobListSections;
  final JobListFilter? filter;

A very similar question was answered 1,5 years ago, but this results in the error The default value of an optional parameter must be constant.

And I guess, if I declare this.jobListSections = const Right([]), I can no longer assign left.

I am assigning the initial value to create the initial state for Bloc.

CodePudding user response：

Because your variables are final you can not change it directly. You can declare copyWith method to change your values.

class JobListState extends Equatable {
  const JobListState({
    this.status = JobListStatus.initial,
    this.jobListSections = Right([]),
    this.filter,
  });

  final JobListStatus status;
  final Either<Failure, List<JobListViewmodel?>> jobListSections;
  final JobListFilter? filter;

  JobListState copyWith({
    JobListStatus? status,
    Either<Failure, List<JobListViewmodel?>>? jobListSections,
    JobListFilter? filter
  }) {
     return JobListState(
       status: status ?? this.status,
       jobListSections: jobListSections ?? this.jobListSections,
       filter: filter ?? this.filter
     );
  }
}

// anywhere you use JobListState
var state = JobListState(); // state.jobListSections is Right([])
state = state.copyWith(jobListSections: Left(Failure())); // state.jobListSections is Left
// here you have new state that you can emit it.