[cdi-dev] Async event proposal

[Jozef Hartinger]

On 06/04/2015 10:08 AM, Antoine Sabot-Durand wrote:
> In our initial proposal fireAsync basic signature was
>
> <U extends T> CompletionStage<U> fireAsync(U event);
>
> I simplified the signature with
>
> CompletionStage<void> fireAsync (U event);
>
> As the original fire method returns void I found confusing to return 
> anything something letting think that a value (different than a 
> status) was obtained from the observers notification.

The reason for the original signature was that it allows the event 
payload to be processed further once all the observers finish. This is 
useful in the common pattern where you fire a mutable event, let the 
(possibly unknown) observers contribute to the result by mutating the 
payload, and then work with the payload when all finish. See e.g. 
https://github.com/weld/core/blob/master/tests-arquillian/src/test/java/org/jboss/weld/tests/experimental/event/async/complex/ComplexAsyncEventTest.java#L74

This of course assumes mutable event payloads are supported.