# Flutter - Wyatt Architecture
The Wyatt Architecture for Flutter.
## Features
- Usecase
- Repository
- DataSource
- Entity
## Usage
### Domain
Create your entities by extending `Entity` :
```dart
class Photo extends Entity {
final int id;
final String url;
const Photo({
required this.id,
required this.url,
});
}
```
Then create the data sources by extending `BaseLocalDataSource` or `BaseRemoteDataSource` depending the type of data source.
```dart
abstract class PhotoRemoteDataSource extends BaseRemoteDataSource {
Future getPhoto(int id);
Future> getAllPhotos({int? start, int? limit});
}
```
Then you can create your repositories by extenting `BaseRepository` :
```dart
abstract class PhotoRepository extends BaseRepository {
FutureResult getPhoto(int id);
FutureResult> getAllPhotos({int? start, int? limit});
}
```
> Here the repository is just a proxy of the data sources with result type (to have beautiful error handling).
And finaly create your different usecases :
Several use cases are supported :
- Classic usecase :
```dart
class Test extends AsyncUseCase>> {
@override
FuturOrResult>> call(QueryParameters? params) {
final photos = _photoRepository.getAllPhotos(
start: params.start,
limit: params.limit,
);
return photos;
}
}
```
You can add alternatve scenarios and check pre/post conditions using our extensions :
```dart
class SearchPhotos extends AsyncUseCase>> {
@override
FutureOrResult>> call(QueryParameters? params) {
final photos = _photoRepository.getAllPhotos(
start: params.start,
limit: params.limit,
);
return photos;
}
@override
FutureOr onStart(QueryParameters? params) {
if(params.start == null || params.limit == null){
throw ClientException('Préconndition non valides');
}
}
}
```
You can implement error scenarios overriding `onError`, or check postconditions by overriding `onComplete` .
- Stream usecase :
```dart
class SearchPhotos extends StreamUseCase>> {
@override
FutureOrResult>>> call(QueryParameters? params) {
final photos = _photoRepository.getAllPhotos(
start: params.start,
limit: params.limit,
);
return photos;
}
}
```
On this case, observers allow you to add alternative scénarios when data changed, overriding `onData` or `onDone`.
Please note that to use handlers, call `call` method and not `execute`.
> In fact, here we need a new parameter object, so let's create it:
```dart
class QueryParameters {
final int? start;
final int? limit;
QueryParameters(this.start, this.limit);
}
```
### Data
We start by creating models for photos and list of photos. You can use `freezed`. The `PhotoModel` extends `Photo` with some de/serializer capabilities. And those are used only in data layer.
Then implements your data sources:
```dart
class PhotoApiDataSourceImpl extends PhotoRemoteDataSource {
final MiddlewareClient _client;
PhotoApiDataSourceImpl(this._client);
@override
Future getPhoto(int id) async {
final response = await _client.get(Uri.parse('/photos/$id'));
final photo =
PhotoModel.fromJson(jsonDecode(response.body) as Map);
return photo;
}
@override
Future> getAllPhotos({int? start, int? limit}) async {
final startQuery = start.isNotNull ? '_start=$start' : '';
final limitQuery = limit.isNotNull ? '_limit=$limit' : '';
final delimiter1 =
(startQuery.isNotEmpty || limitQuery.isNotEmpty) ? '?' : '';
final delimiter2 =
(startQuery.isNotEmpty && limitQuery.isNotEmpty) ? '&' : '';
final url = '/photos$delimiter1$startQuery$delimiter2$limitQuery';
final response = await _client.get(Uri.parse(url));
final photos =
ListPhotoModel.fromJson({'photos': jsonDecode(response.body)});
return photos.photos;
}
}
```
> 1: Note that here we use `MiddlewareClient` from our http package.
> 2: You can create multiple implementations (one real and one mock for example).
And implement the repositories:
```dart
class PhotoRepositoryImpl extends PhotoRepository {
final PhotoRemoteDataSource _photoRemoteDataSource;
PhotoRepositoryImpl(
this._photoRemoteDataSource,
);
@override
FutureResult getPhoto(int id) => Result.tryCatchAsync(
() => _photoRemoteDataSource.getPhoto(id),
(error) => ServerException('Cannot retrieve photo $id.'),
);
@override
FutureResult> getAllPhotos({int? start, int? limit}) async =>
Result.tryCatchAsync(
() => _photoRemoteDataSource.getAllPhotos(start: start, limit: limit),
(error) => ServerException('Cannot retrieve all photos.'),
);
}
```
That's all.