how to implement toFuture from AsyncState

[yousefak007]

is this correct?

extension SignalAsyncStateExtensions<T> on ReadonlySignal<AsyncState<T>> {
  Future<T> toFuture() async {
    final completer = Completer<T>();

    EffectCleanup? disposer;

    completer.future.whenComplete(() {
      disposer?.call();
    }).ignore();

    disposer = subscribe((value) {
      if (value is AsyncData) {
        completer.complete(value.requireValue);
      } else if (value is AsyncError) {
        completer.completeError(value.error!, value.stackTrace);
      }
    });

    onDispose(() {
      disposer?.call();
    });

    return completer.future;
  }
}

[jinyus]

You aren't covering a few edge cases.

Memory Pressure

Calling this multiple times will create new completer instances and subscriptions. You probably want cache the completer.

Eagerness

Subscriptions are eager so the future will be completed immediately with the current value/error, you probably want to wait for the next value.

Signal is disposed before a value is emitted.

If this happens, the future will wait indefinitely. You should complete with an error or with the current value in the ondispose callback.

[yousefak007]

Memory Pressure
Calling this multiple times will create new completer instances and subscriptions. You probably want cache the completer.

currently yes, every instance has its own complete, maybe expando or weak reference should solve this

Eagerness
Subscriptions are eager so the future will be completed immediately with the current value/error, you probably want to wait for the next value.

i want to evaluate the value immediately if it already has value or error

[yousefak007]

edit: after improvements

extension SignalAsyncStateExtensions<T> on ReadonlySignal<AsyncState<T>> {
  Future<T> toFuture() async {
    Completer<T>? completer = Completer<T>();

    // register disposers

    EffectCleanup? disposer;

    // when signal disposed before future finished
    onDispose(() {
      disposer?.call();

      if (completer?.isCompleted == false) {
        completer!.completeError('future not completed');
      }

      completer = null;
    });

    // when future finished and signal still alive
    completer!.future.whenComplete(() {
      disposer?.call();
      completer = null;
    }).ignore();

    disposer = subscribe((value) => _toFuture(completer!, value));

    return completer!.future;
  }

  static void _toFuture<T>(Completer<T> completer, AsyncState<T> value) {
    if (value is AsyncData) {
      completer.complete(value.requireValue);
    } else if (value is AsyncError) {
      completer.completeError(value.error!, value.stackTrace);
    }
  }
}

[yousefak007]

i don't know how i can remove it or cancel it 😥

[jinyus]

I posted the code above. onDispose returns a function to unregister to callback.

#198 (reply in thread)

[yousefak007]

onDispose is void

[jinyus]

Oh, sorry about that. I added that feature last week and it hasn't been released as yet. You can use your approach until the next release.

signals.dart/packages/signals_core/lib/src/core/signal.dart

Line 116 in 663786e

EffectCleanup onDispose(void Function() cleanup);

[rodydavis]

Yep going to release soon, probably today or tomorrow