docs(architecture): update Readme. (#38)

packages/wyatt_architecture/README.md

@@ -31,10 +31,10 @@ The Wyatt Architecture for Flutter.
 
 ## Features
 
-* Usecase
+- Usecase
-* Repository
+- Repository
-* DataSource
+- DataSource
-* Entity
+- Entity
 
 ## Usage
 
@@ -75,16 +75,17 @@ abstract class PhotoRepository extends BaseRepository {
 
 > 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 by using `UseCase<Parameters, ReturnType>` :
+And finaly create your different usecases :
+
+Several use cases are supported :
+
+- Classic usecase :
 
 ```dart
-class RetrieveAllPhoto extends UseCase<QueryParameters, List<Photo>> {
+class Test extends AsyncUseCase<QueryParameters, List<Photo>>> {
-  final PhotoRepository _photoRepository;
-
-  RetrieveAllPhotos(this._photoRepository);
 
   @override
-  FutureResult<List<Photo>> call(QueryParameters params) {
+  FuturOrResult<List<Photo>>> call(QueryParameters? params) {
      final photos = _photoRepository.getAllPhotos(
       start: params.start,
       limit: params.limit,
@@ -94,6 +95,54 @@ class RetrieveAllPhoto extends UseCase<QueryParameters, List<Photo>> {
 }
 ```
 
+You can add alternatve scenarios and check pre/post conditions using our extensions :
+
+```dart
+class SearchPhotos extends AsyncUseCase<QueryParameters, List<Photo>>> {
+
+  @override
+  FutureOrResult<List<Photo>>> call(QueryParameters? params) {
+     final photos = _photoRepository.getAllPhotos(
+      start: params.start,
+      limit: params.limit,
+    );
+    return photos;
+  }
+
+
+  @override
+  FutureOr<void> 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<QueryParameters, List<Photo>>> {
+
+  @override
+  FutureOrResult<Stream<List<Photo>>>> 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 `execute` methodes instead of `call`.
+
 > In fact, here we need a new parameter object, so let's create it:
 
 ```dart