---
title: Domain
description: The note entity and the repository port, with no Flutter import.
tags: [clean-architecture, flutter]
---

In this track the entity lives at `lib/features/notes/domain/`. `ValidationFailure` lives in `lib/shared/`, outside the feature, so a second feature can throw the same type without importing notes.

A note has an identity, a title, and a body. `Note.create` is the constructor that checks the title. It trims the title and the body. A blank title throws `ValidationFailure('Title is required')` before any repository is involved. The row mapper rebuilds with the field constructor. The title rule has already run on `create`.

```dart
factory Note.create({
  required String id,
  required String title,
  required String body,
  required DateTime createdAt,
}) {
  final trimmed = title.trim();
  if (trimmed.isEmpty) {
    throw const ValidationFailure('Title is required');
  }
  return Note(
    id: id,
    title: trimmed,
    body: body.trim(),
    createdAt: createdAt,
  );
}
```

`NoteRepository` is the port: `save` and `findAll`. It returns notes, not rows. The entity is [`lib/features/notes/domain/note.dart`](https://github.com/newtalaria/clean-architecture/blob/main/examples/flutter/feature_first/lib/features/notes/domain/note.dart). The port is [`lib/features/notes/domain/note_repository.dart`](https://github.com/newtalaria/clean-architecture/blob/main/examples/flutter/feature_first/lib/features/notes/domain/note_repository.dart). [`lib/shared/validation_failure.dart`](https://github.com/newtalaria/clean-architecture/blob/main/examples/flutter/feature_first/lib/shared/validation_failure.dart) sits outside the feature so the next feature can use the same failure.

Nothing in the domain folder imports Flutter, Riverpod, Beamer, or the data implementation. That is the dependency rule for this track, same as the others.

Next: [Application](application.md).