when should we use freezed as sealed classes or constructor?


Which way to use freezed library with bloc ? first one as a sealed classes, the other is a constructor.

First way

abstract class HomeState with _$HomeState {
  const factory HomeState.initial() = _Initial;
  const factory HomeState.addNewNoteButtonClicked(@Default(false)  bool isClicked) = AddNewNoteClicked;
  factory HomeState.addNewNote( Note value) = AddNewNote;

Second Way:

abstract class HomeState with _$HomeState {
  const factory HomeState({
    required Note value,
    required bool isClicked,
  }) = AddNewNoteClicked;
  factory HomeState.init() => HomeState(
        value: Note(value: ''),
        isClicked: false,


TL;DR: I think there is no correct way, just what works for you.

When using freezed, every factory constructor generates a separate class. Together with that, it generates some convenience methods, like map/maybeMap/when/maybeWhen. This is very convenient when your BLoC has obvious and different states and you want to handle your UI accordingly. For instance: initial, loadInProgress, loadSuccess, loadFailure. Then, in your UI, you could use something like:

class Example extends StatelessWidget {
  const Example();

  Widget build(BuildContext context) {
    return BlocBuilder<ExampleCubit, ExampleState>(
      builder: (_, state) => state.maybeWhen(
        loadInProgress: () => const LoaderView(),
        loadFailure: () => const ErrorView(),
        loadSuccess: (categories) => const SomeView(),
        orElse: () => const SizedBox(),

However, it also brings some inconvenience when you need to take data from the specific state: you must check if the state is a specific one and only then you can process with your code, e.g:

if (state is ExampleStateSuccess) {

In such cases, when you need to have just a single state but a lot of different properties (a good example would be form validation when you store all the field properties in your BLoC and you want to validate/update them, submit the form later) it is better to use a single state with properties. By better, I mean it’s just easier this way.

Answered By – mkobuolys

Answer Checked By – Pedro (FlutterFixes Volunteer)

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