diff --git a/packages/wyatt_architecture/example/lib/data/repositories/photo_repository_impl.dart b/packages/wyatt_architecture/example/lib/data/repositories/photo_repository_impl.dart
index 3f85aff2..7cec10fa 100644
--- a/packages/wyatt_architecture/example/lib/data/repositories/photo_repository_impl.dart
+++ b/packages/wyatt_architecture/example/lib/data/repositories/photo_repository_impl.dart
@@ -35,46 +35,47 @@ class PhotoRepositoryImpl extends PhotoRepository {
   );
 
   @override
-  FutureResult<void> addPhotoToFavorites(Photo photo) => Result.tryCatchAsync(
+  FutureOrResult<void> addPhotoToFavorites(Photo photo) => Result.tryCatchAsync(
         () => _favoriteLocalDataSource.addPhotoToFavorites(photo),
         (error) => ClientException('Cannot add photo to favorites.'),
       );
 
   @override
-  FutureResult<bool> checkIfPhotoIsInFavorites(int id) => Result.tryCatchAsync(
+  FutureOrResult<bool> checkIfPhotoIsInFavorites(int id) =>
+      Result.tryCatchAsync(
         () => _favoriteLocalDataSource.checkIfPhotoIsInFavorites(id),
         (error) =>
             ClientException('Cannot check if photo `$id` is in favorites.'),
       );
 
   @override
-  FutureResult<void> deletePhotoFromFavorites(int id) => Result.tryCatchAsync(
+  FutureOrResult<void> deletePhotoFromFavorites(int id) => Result.tryCatchAsync(
         () => _favoriteLocalDataSource.deletePhotoFromFavorites(id),
         (error) => ClientException('Cannot delete photo `$id` from favorites.'),
       );
 
   @override
-  FutureResult<Album> getAlbum(int id) => Result.tryCatchAsync(
+  FutureOrResult<Album> getAlbum(int id) => Result.tryCatchAsync(
         () => _albumRemoteDataSource.getAlbum(id),
         (error) => ServerException('Cannot retrieve album $id.'),
       );
 
   @override
-  FutureResult<List<Album>> getAllAlbums({int? start, int? limit}) =>
+  FutureOrResult<List<Album>> getAllAlbums({int? start, int? limit}) =>
       Result.tryCatchAsync(
         () => _albumRemoteDataSource.getAllAlbums(start: start, limit: limit),
         (error) => ServerException('Cannot retrieve all albums.'),
       );
 
   @override
-  FutureResult<List<Photo>> getAllPhotos({int? start, int? limit}) async =>
+  FutureOrResult<List<Photo>> getAllPhotos({int? start, int? limit}) async =>
       Result.tryCatchAsync(
         () => _photoRemoteDataSource.getAllPhotos(start: start, limit: limit),
         (error) => ServerException('Cannot retrieve all photos.'),
       );
 
   @override
-  FutureResult<List<Photo>> getAllPhotosFromFavorites() async {
+  FutureOrResult<List<Photo>> getAllPhotosFromFavorites() async {
     try {
       final response = <Photo>[];
       final favorites =
@@ -95,13 +96,13 @@ class PhotoRepositoryImpl extends PhotoRepository {
   }
 
   @override
-  FutureResult<Photo> getPhoto(int id) => Result.tryCatchAsync(
+  FutureOrResult<Photo> getPhoto(int id) => Result.tryCatchAsync(
         () => _photoRemoteDataSource.getPhoto(id),
         (error) => ServerException('Cannot retrieve photo $id.'),
       );
 
   @override
-  FutureResult<List<Photo>> getPhotosFromAlbum(
+  FutureOrResult<List<Photo>> getPhotosFromAlbum(
     int albumId, {
     int? start,
     int? limit,
diff --git a/packages/wyatt_architecture/example/lib/domain/repositories/photo_repository.dart b/packages/wyatt_architecture/example/lib/domain/repositories/photo_repository.dart
index b57b4689..7bc195ea 100644
--- a/packages/wyatt_architecture/example/lib/domain/repositories/photo_repository.dart
+++ b/packages/wyatt_architecture/example/lib/domain/repositories/photo_repository.dart
@@ -19,17 +19,17 @@ import 'package:architecture_example/domain/entities/photo.dart';
 import 'package:wyatt_architecture/wyatt_architecture.dart';
 
 abstract class PhotoRepository extends BaseRepository {
-  FutureResult<Album> getAlbum(int id);
-  FutureResult<List<Album>> getAllAlbums({int? start, int? limit});
-  FutureResult<Photo> getPhoto(int id);
-  FutureResult<List<Photo>> getAllPhotos({int? start, int? limit});
-  FutureResult<List<Photo>> getPhotosFromAlbum(
+  FutureOrResult<Album> getAlbum(int id);
+  FutureOrResult<List<Album>> getAllAlbums({int? start, int? limit});
+  FutureOrResult<Photo> getPhoto(int id);
+  FutureOrResult<List<Photo>> getAllPhotos({int? start, int? limit});
+  FutureOrResult<List<Photo>> getPhotosFromAlbum(
     int albumId, {
     int? start,
     int? limit,
   });
-  FutureResult<void> addPhotoToFavorites(Photo photo);
-  FutureResult<void> deletePhotoFromFavorites(int id);
-  FutureResult<List<Photo>> getAllPhotosFromFavorites();
-  FutureResult<bool> checkIfPhotoIsInFavorites(int id);
+  FutureOrResult<void> addPhotoToFavorites(Photo photo);
+  FutureOrResult<void> deletePhotoFromFavorites(int id);
+  FutureOrResult<List<Photo>> getAllPhotosFromFavorites();
+  FutureOrResult<bool> checkIfPhotoIsInFavorites(int id);
 }
diff --git a/packages/wyatt_architecture/example/lib/domain/usecases/photos/add_photo_to_favorites.dart b/packages/wyatt_architecture/example/lib/domain/usecases/photos/add_photo_to_favorites.dart
index 7e88cdc3..7a936d44 100644
--- a/packages/wyatt_architecture/example/lib/domain/usecases/photos/add_photo_to_favorites.dart
+++ b/packages/wyatt_architecture/example/lib/domain/usecases/photos/add_photo_to_favorites.dart
@@ -1,31 +1,40 @@
 // Copyright (C) 2022 WYATT GROUP
 // Please see the AUTHORS file for details.
-// 
+//
 // This program is free software: you can redistribute it and/or modify
 // it under the terms of the GNU General Public License as published by
 // the Free Software Foundation, either version 3 of the License, or
 // any later version.
-// 
+//
 // This program is distributed in the hope that it will be useful,
 // but WITHOUT ANY WARRANTY; without even the implied warranty of
 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 // GNU General Public License for more details.
-// 
+//
 // You should have received a copy of the GNU General Public License
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
+import 'dart:async';
+
 import 'package:architecture_example/domain/entities/photo.dart';
 import 'package:architecture_example/domain/repositories/photo_repository.dart';
 import 'package:wyatt_architecture/wyatt_architecture.dart';
 
-class AddPhotoToFavorites extends UseCase<Photo, List<Photo>> {
+class AddPhotoToFavorites extends AsyncUseCase<Photo, List<Photo>> {
   final PhotoRepository _photoRepository;
 
   AddPhotoToFavorites(this._photoRepository);
 
   @override
-  FutureResult<List<Photo>> call(Photo params) async {
-    await _photoRepository.addPhotoToFavorites(params);
+  FutureOrResult<List<Photo>> call(Photo? params) async {
+    await _photoRepository.addPhotoToFavorites(params!);
     return _photoRepository.getAllPhotosFromFavorites();
   }
+
+  @override
+  FutureOr<void> onStart(Photo? params) {
+    if (params == null) {
+      throw ClientException('Photo cannot be null');
+    }
+  }
 }
diff --git a/packages/wyatt_architecture/example/lib/domain/usecases/photos/check_if_photo_is_in_favorites.dart b/packages/wyatt_architecture/example/lib/domain/usecases/photos/check_if_photo_is_in_favorites.dart
index d955d4f1..1bb9efd9 100644
--- a/packages/wyatt_architecture/example/lib/domain/usecases/photos/check_if_photo_is_in_favorites.dart
+++ b/packages/wyatt_architecture/example/lib/domain/usecases/photos/check_if_photo_is_in_favorites.dart
@@ -14,15 +14,24 @@
 // You should have received a copy of the GNU General Public License
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
+import 'dart:async';
+
 import 'package:architecture_example/domain/repositories/photo_repository.dart';
 import 'package:wyatt_architecture/wyatt_architecture.dart';
 
-class CheckIfPhotoIsInFavorites extends UseCase<int, bool> {
+class CheckIfPhotoIsInFavorites extends AsyncUseCase<int, bool> {
   final PhotoRepository _photoRepository;
 
   CheckIfPhotoIsInFavorites(this._photoRepository);
 
   @override
-  FutureResult<bool> call(int params) async =>
-      _photoRepository.checkIfPhotoIsInFavorites(params);
+  FutureOrResult<bool> call(int? params) async =>
+      _photoRepository.checkIfPhotoIsInFavorites(params!);
+
+  @override
+  FutureOr<void> onStart(int? params) {
+    if (params == null) {
+      throw ClientException('id cannot be null');
+    }
+  }
 }
diff --git a/packages/wyatt_architecture/example/lib/domain/usecases/photos/display_favorites.dart b/packages/wyatt_architecture/example/lib/domain/usecases/photos/display_favorites.dart
index 545c09e5..733e2dbd 100644
--- a/packages/wyatt_architecture/example/lib/domain/usecases/photos/display_favorites.dart
+++ b/packages/wyatt_architecture/example/lib/domain/usecases/photos/display_favorites.dart
@@ -1,16 +1,16 @@
 // Copyright (C) 2022 WYATT GROUP
 // Please see the AUTHORS file for details.
-// 
+//
 // This program is free software: you can redistribute it and/or modify
 // it under the terms of the GNU General Public License as published by
 // the Free Software Foundation, either version 3 of the License, or
 // any later version.
-// 
+//
 // This program is distributed in the hope that it will be useful,
 // but WITHOUT ANY WARRANTY; without even the implied warranty of
 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 // GNU General Public License for more details.
-// 
+//
 // You should have received a copy of the GNU General Public License
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
@@ -18,13 +18,13 @@ import 'package:architecture_example/domain/entities/photo.dart';
 import 'package:architecture_example/domain/repositories/photo_repository.dart';
 import 'package:wyatt_architecture/wyatt_architecture.dart';
 
-class DisplayFavorites extends UseCase<void, List<Photo>> {
+class DisplayFavorites extends AsyncUseCase<NoParam, List<Photo>> {
   final PhotoRepository _photoRepository;
 
   DisplayFavorites(this._photoRepository);
 
   @override
-  FutureResult<List<Photo>> call(void params) {
+  FutureOrResult<List<Photo>> call(void params) {
     final photos = _photoRepository.getAllPhotosFromFavorites();
     return photos;
   }
diff --git a/packages/wyatt_architecture/example/lib/domain/usecases/photos/display_photo.dart b/packages/wyatt_architecture/example/lib/domain/usecases/photos/display_photo.dart
index 3c5da43d..3a41eeb2 100644
--- a/packages/wyatt_architecture/example/lib/domain/usecases/photos/display_photo.dart
+++ b/packages/wyatt_architecture/example/lib/domain/usecases/photos/display_photo.dart
@@ -14,18 +14,27 @@
 // You should have received a copy of the GNU General Public License
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
+import 'dart:async';
+
 import 'package:architecture_example/domain/entities/photo.dart';
 import 'package:architecture_example/domain/repositories/photo_repository.dart';
 import 'package:wyatt_architecture/wyatt_architecture.dart';
 
-class DisplayPhoto extends UseCase<int, Photo> {
+class DisplayPhoto extends AsyncUseCase<int, Photo> {
   final PhotoRepository _photoRepository;
 
   DisplayPhoto(this._photoRepository);
 
   @override
-  FutureResult<Photo> call(int params) {
-    final photo = _photoRepository.getPhoto(params);
+  FutureOrResult<Photo> call(int? params) {
+    final photo = _photoRepository.getPhoto(params!);
     return photo;
   }
+
+  @override
+  FutureOr<void> onStart(int? params) {
+    if (params == null) {
+      throw ClientException('id cannot be null');
+    }
+  }
 }
diff --git a/packages/wyatt_architecture/example/lib/domain/usecases/photos/open_album.dart b/packages/wyatt_architecture/example/lib/domain/usecases/photos/open_album.dart
index 926d5331..a1053a15 100644
--- a/packages/wyatt_architecture/example/lib/domain/usecases/photos/open_album.dart
+++ b/packages/wyatt_architecture/example/lib/domain/usecases/photos/open_album.dart
@@ -14,24 +14,33 @@
 // You should have received a copy of the GNU General Public License
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
+import 'dart:async';
+
 import 'package:architecture_example/domain/entities/photo.dart';
 import 'package:architecture_example/domain/repositories/photo_repository.dart';
 import 'package:architecture_example/domain/usecases/photos/params/query_parameters.dart';
 import 'package:wyatt_architecture/wyatt_architecture.dart';
 
-class OpenAlbum extends UseCase<QueryParameters, List<Photo>> {
+class OpenAlbum extends AsyncUseCase<QueryParameters, List<Photo>> {
   final PhotoRepository _photoRepository;
 
   OpenAlbum(this._photoRepository);
 
   @override
-  FutureResult<List<Photo>> call(QueryParameters params) {
+  FutureOrResult<List<Photo>> call(QueryParameters? params) {
     final photos = _photoRepository.getPhotosFromAlbum(
-      params.albumId,
+      params!.albumId,
       start: params.start,
       limit: params.limit,
     );
 
     return photos;
   }
+
+  @override
+  FutureOr<void> onStart(QueryParameters? params) {
+    if (params == null) {
+      throw ClientException('params cannot be null');
+    }
+  }
 }
diff --git a/packages/wyatt_architecture/example/lib/domain/usecases/photos/remove_photo_from_favorites.dart b/packages/wyatt_architecture/example/lib/domain/usecases/photos/remove_photo_from_favorites.dart
index 90012646..e706beea 100644
--- a/packages/wyatt_architecture/example/lib/domain/usecases/photos/remove_photo_from_favorites.dart
+++ b/packages/wyatt_architecture/example/lib/domain/usecases/photos/remove_photo_from_favorites.dart
@@ -14,18 +14,27 @@
 // You should have received a copy of the GNU General Public License
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
+import 'dart:async';
+
 import 'package:architecture_example/domain/entities/photo.dart';
 import 'package:architecture_example/domain/repositories/photo_repository.dart';
 import 'package:wyatt_architecture/wyatt_architecture.dart';
 
-class RemovePhotoFromFavorites extends UseCase<int, List<Photo>> {
+class RemovePhotoFromFavorites extends AsyncUseCase<int, List<Photo>> {
   final PhotoRepository _photoRepository;
 
   RemovePhotoFromFavorites(this._photoRepository);
 
   @override
-  FutureResult<List<Photo>> call(int params) async {
-    await _photoRepository.deletePhotoFromFavorites(params);
+  FutureOrResult<List<Photo>> call(int? params) async {
+    await _photoRepository.deletePhotoFromFavorites(params!);
     return _photoRepository.getAllPhotosFromFavorites();
   }
+
+  @override
+  FutureOr<void> onStart(int? params) {
+    if (params == null) {
+      throw ClientException('id cannot be null');
+    }
+  }
 }
diff --git a/packages/wyatt_architecture/example/lib/domain/usecases/photos/retrieve_all_albums.dart b/packages/wyatt_architecture/example/lib/domain/usecases/photos/retrieve_all_albums.dart
index c8a02e86..560abe93 100644
--- a/packages/wyatt_architecture/example/lib/domain/usecases/photos/retrieve_all_albums.dart
+++ b/packages/wyatt_architecture/example/lib/domain/usecases/photos/retrieve_all_albums.dart
@@ -14,22 +14,31 @@
 // You should have received a copy of the GNU General Public License
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
+import 'dart:async';
+
 import 'package:architecture_example/domain/entities/album.dart';
 import 'package:architecture_example/domain/repositories/photo_repository.dart';
 import 'package:architecture_example/domain/usecases/photos/params/query_parameters.dart';
 import 'package:wyatt_architecture/wyatt_architecture.dart';
 
-class RetrieveAllAlbums extends UseCase<QueryParameters, List<Album>> {
+class RetrieveAllAlbums extends AsyncUseCase<QueryParameters, List<Album>> {
   final PhotoRepository _photoRepository;
 
   RetrieveAllAlbums(this._photoRepository);
 
   @override
-  FutureResult<List<Album>> call(QueryParameters params) {
+  FutureOrResult<List<Album>> call(QueryParameters? params) {
     final albums = _photoRepository.getAllAlbums(
-      start: params.start,
+      start: params!.start,
       limit: params.limit,
     );
     return albums;
   }
+
+  @override
+  FutureOr<void> onStart(QueryParameters? params) {
+    if (params == null) {
+      throw ClientException('params cannot be null');
+    }
+  }
 }