so far everything seemed to work fine, but there's one error that I get now:
.shareValue() doesn't exist anymore
Ah!
Since it's an extension I need to import rxdart for it to exist.
Got it :)
Great job! Thanks for also providing the codemod
One suggestion though: add the
.seeded() factory constructor to the codemod
I had to replace all of this manually
I have a common usage where I want a ValueStream which doesn't shut down when it no longer has listeners. You could imagine that you have a global ValueStream for a Firestore document, and you never want this stream to close due to changes in the number of subscribers, e.g. The workaround I have right now is to register a no-op listener upon creation of the ValueStream, which then "tricks" the stream into thinking it always has a listener. Is there a better pattern I could adopt for this?
@jackdreilly since rxdart is built upon the Dart Streams, a ValueStream is like a broadcast Stream, see https://api.flutter.dev/flutter/dart-async/StreamController/StreamController.broadcast.html
So no, to prevent onCancel, a dummy listener could be a solution in your case
I'm still being surprised by the behaviour of
ValueStream :-/
Like, you do this:
newStream = old.map(mapping).shareValue(mapping);
old.add('foo');
newStream.value == 'foo'; // That's not the case
So, unless anyone is listening to the stream, it won't update
.value properly
Or is this problem going to persist
Hi. I've just started implementing the bloc library in my app, and used their example for a form. I've realised this issue: felangel/bloc#1888
Could somebody help me find a solution to do this properly?
So basically, there are events that represent an input field change (
EmailChanged and PasswordChanged events)
To avoid rebuilding the form and doing unnecessary validations, these are debounced:
final debounced = events
.where((event) => event is! FormSubmitted)
.debounceTime(const Duration(milliseconds: 300));
They are then merged with the
FormSubmitted event like this:
return events
.where((event) => event is FormSubmitted)
.mergeWith([debounced])
The problem with that is, that
EmailChangedand PasswordChanged events could be triggered, being debounced, and then the FormSubmitted event could arrive, and be handled before the change events are being handled
You could go with combineLatest or switchMap for starters, can the submit only happen when both fields are valid?
This is very rough, and can be improved, but the idea is that any change to either field would reset the sequence to valid = false and would block submit.
final onEmail = PublishSubject<String>(),
onPassword = PublishSubject<String>();
final onSubmit = PublishSubject<bool>();
final email = onEmail.debounceTime(const Duration(seconds: 1)),
password = onPassword.debounceTime(const Duration(seconds: 1));
bool Function(String) validateEmail, validatePassword;
final onSyncInput = Rx.merge([onEmail, onPassword]);
final onValid = Rx.combineLatest2(email.map(validateEmail),
password.map(validatePassword), (e, p) => e && p);
onSyncInput
.switchMap((_) => onValid)
.switchMap((canSubmit) => canSubmit ? onSubmit : Stream.value(false));
But if the AuthUser stream emits another item, which means another user has signed in, i need to automatically make sure the UserProfile stream switches as well
how can i achieve such functionality>
I think I need a way of transforming a stream into another stream, and if the original stream emits another item, the downstream stream needs to see it and change.
So your choice depends, do you only care for the very latest event in the original stream? Then use switchMap. Do you want to handle every event? Use the others, with flatMap, the downstream emits whenever a transformation is completed, with asyncExpand, it will await each transformation and emit.
