async TypedMiddleware?

[MihaMarkic]

It'd be nice to have async versions of TypedMiddleware.

return (Store<AppState> store, LoginResultAction action, Future<NextDispatcher> next) async {
    await next(action);
    ....

So the next dispatcher can be awaited.
Does that make sense?

[brianegan]

Hey there -- sorry, thought I'd put in an answer to that Q!

Could you describe the use-case a bit more to see if we can find a good solution?

Overall, I definitely understand why this would be helpful, but this would essentially break the fundamental promise that Redux gives you: Actions are dispatched and reduced synchronously.

This means you can do store.dispatch on one line, and the very next line store.state will be in the expected state given the update. If we made next async, this means any action in the chain could delay the reducer from running synchronously, and I think that will lead to a lot more headaches.

[MihaMarkic]

I see. I was thinking about what if you have to execute an async operation within middleware, such as if you want to persist the current state and the persistence method is asynchronous? Or perhaps you need some other async method to proceed? Isn't this something that middleware should support? Or not?

[brianegan]

Isn't this something that middleware should support? Or not?

It certainly is! The main trick: You can't use async/await, but you can still do myFuture.then(...).then(...) or listen to Streams just fine.

That said, if you'd like to use async/await or Streams in middleware, lot of times I'll use the redux_epics package. It's kind of like Stream-based middleware, and it supports async* functions which allow you to run async/await calls.

https://pub.dartlang.org/packages/redux_epics

[MihaMarkic]

Basically calling async methods without waiting, I guess it makes sense.