Combining flutter bloc forEach() with another await

Question

Imagine I've got a (contrived) state that looks something like:

class UserState {
  final String? name;
  final String? address;
}

The source for name comes from a single (asynchronous) API call, but the address field value comes from a stream. Conceptually, the bloc might emit the following:

UserState(name: null,   address: null)
UserState(name: null,   address: 'New York')
UserState(name: 'john', address: 'New York')
UserState(name: 'john', address: 'Smith St, New York')
UserState(name: 'john', address: '10 Smith St, New York')

The screen that receives these states is perfectly capable of rendering itself based on the presence (or not) of name and address.

I can see that there's emit.forEach() that looks like it would be perfect for dealing with the stream, but I'm wrestling with how to deal with awaiting for the fetchName() API call.

I thought of having a local variable which keep track of whether name has came back (something like the following) but there's a scenario where fetchName() is slow and doesn't return until after all the address stream events have finished - which means I miss a state.

on<FetchUserEvent>((event, emit) async {
  String? name;
  fetchName().then((n) => name = n);

  emit.forEach(
    addressStream,
    onData: (a) => UserState(name: name, address: a)
  );
});

Is my only option to have to import RxDart just to pick up something like "combine latest"?

Am I "doing it wrong"?

Answer 1

on<FetchUserEvent>((event, emit) async {
  String? name = await fetchName();

  emit.forEach(
    addressStream,
    onData: (a) => UserState(name: name, address: a)
  );
});