Prism: Support for async subscribers in the EventAggregator.

[ylatuya]

Hi,

One of the main issues we found with the EventAggregator implementation is that it does not supports async subscribers. We have added support for that so one can now do:

void Subscribe () {
  EventAggregator.GetEvent<PubSubEvent<SaveProjectEvent>> ().SubscribeAsync (HandleSave);
}

async Task HandleSave (SaveProjectEvent saveEvent){
  saveEvent.ReturnValue = await AsyncTask();
}

void Save () {
  var saveEvent = new SaveProjectEvent (project;
  await  EventAggregator.GetEvent<PubSubEvent<SaveProjectEvent>> ().Publish (saveEvent);
  if (saveEvent.ReturnValue) {
     InfoMessage ("Success");
  }
}

This changes slightly the API, with Publish returning a Task and adding a new SubscribeAsync function, but I think the change makes the events aggregator much more useful.
Would you consider a change like that? In that case we can work on the PR.

[brianlagunas]

Thanks for the idea, but this is not something we will be adding to Prism. The even aggregator is fire and forget.

[molinch]

@ylatuya would you mind sharing your implementation for PublishAsync?

[ylatuya]

You can find the implementation here with the commit adding support for Async on top of Prism

[molinch]

Thanks ! I took a different approach in our project, which doesn't involve touching Prism classes, but being on top of them. If I find time I can try to share it.

[brinko99]

I too am interested in such functionality. @molinch, might you be able to share your solution?

I've successfully used the Deferral solution provided by Stephen Cleary. It requires adding a Deferral to the PubSubEvent payload that can be awaited on. It works great, but the syntax is clunky for users and implementers.

[lock[bot]]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.