如何Either在以下代碼中正確初始化我的物件？
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;
1,5 年前回答了一個非常相似的問題，但這會導致錯誤The default value of an optional parameter must be constant.
而且我想，如果我宣告this.jobListSections = const Right([])，我就不能再分配 left 了。
我正在分配初始值以創建 Bloc 的初始狀態。
uj5u.com熱心網友回復：
因為你的變數是final你不能直接改變它。您可以宣告copyWith更改值的方法。
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.
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