Generic Usecase Flutter

Hello everyone! Today, I want to show you the usage of generic usecases in flutter with riverpod.

Base UseCase

We will start with usecase.

Creating base usecase

Firstly, we need to create a base class for usecase, and we will extend it for different usecases.

dart
abstract class UseCaseBase<T, Params> {
  const UseCaseBase();
}

We also need no-params class. It's an optional class. You don't need to use it every time.

For no parameters:

dart
class NoParams {}

Creating base usecases for `Future` and `Stream`

For Future:

dart
abstract class FutureUseCase<T, Params> extends UseCaseBase<T, Params> {
  const FutureUseCase();
 
  Future<T> call(Params params);
}

And for Stream:

dart
abstract class StreamUseCase<T, Params> extends UseCaseBase<T, Params> {
  const StreamUseCase();
 
  Stream<T> call(Params params);
}

So now, we have usecases for Stream case and Future case.

Usage

We will apply the above usecase where we need. Firstly, if you want to create getting posts from database usecase, we should use Stream for returning data.

GetPosts Usecase

dart
class GetPosts implements StreamUseCase<List<Post>>, NoParams> {
  final PostRepository repo;
 
  const GetPosts(this.repo);
 
  @override
  Stream<List<Post>> call(NoParams params) => repo.watchAllPosts();
}

But, if you want to use just Future,

dart
class GetPosts implements FutureUseCase<List<Post>>, NoParams> {
  final PostRepository repo;
 
  const GetPosts(this.repo);
 
  @override
  Future<List<Post>> call(NoParams params) => repo.getAllPosts();
}

CreatePost Usecase

Let's create a post. Firstly, we need some parameters to create post.

dart
class CreatePostParams {
  final String title;
  final String? description;
  final String author;
 
  const CreatePostParams({
    required this.title,
    this.description,
    required this.author,
  });
}

And then, create a usecase for creating post.

dart
class CreatePost implements FutureUseCase<Post?>, CreatePostParams> {
  final PostRepository repo;
 
  const CreatePost(this.repo);
 
  @override
  Future<Post?> call(CreatePostParams params) async {
    return repo.createPost(
        title: params.title,
        description: params.description,
        author: params.author,
    );
  }
}

The last thing we need to do is using in our presentation layer or application layer if you are using application layer separately.

I will show you in next article for this usage in presentation layer. Thank you for reading my blogs.