Application

lib/features/notes/application/. The use case imports the feature's own port. It does not import another feature.

SaveNoteUseCase.execute builds a note with Note.create, asks the port to save it, and returns that note. The repository's save returns nothing, so the caller sees the DateTime the use case passed in. ListNotesUseCase returns whatever findAll mapped from the rows.

The clock and the id generator are constructor arguments, so a test can pin both. A blank title throws from Note.create. The notifier turns that failure into the string under the form.

Future<Note> execute({required String title, required String body}) async {
  final note = Note.create(
    id: _ids.next(),
    title: title,
    body: body,
    createdAt: _clock.now(),
  );
  await _notes.save(note);
  return note;
}

The file is lib/features/notes/application/save_note_use_case.dart.

The use case imports the port, Clock, and IdGenerator. SystemClock and SequentialIdGenerator live in those same files. The composition root is the file that names them. The notifier calls the use case through the providers. The page watches notesProvider.

Next: Data.