On Friday, December 6, 2019 at 9:20:21 AM UTC+11, Geoff Lankow wrote:
> Hi all
>
> I'm redesigning a bunch of Thunderbird things to be asynchronous. I'd
> like to use Promises but a lot of the time I'll be far from a JS context
> so that doesn't really seem like an option. The best alternative I've
> come up with is to create some sort of listener object and pass it to
> the async function:
>
> interface nsIFooOperationListener : nsISupports {
> void onOperationComplete(
> in nsresult status,
> [optional] in string errorMessage
> );
> };
>
> ...
>
> void fooFunction(..., in nsIFooOperationListener listener);
>
> This works fine but I wonder if there's a better way, or if there's some
> established prior art I can use/borrow rather than find out the pitfalls
> myself.
>
> TIA,
> GL
We have mozilla::MozPromise [0], similar to mozilla::dom::Promise but it
doesn't rely on JS at all.
It can be a bit tricky to use, the simplest way (to start) is probably to do
something like InvokeAsync(work thread, code to run that resolves or rejects
the promise)->Then(target thread, on-success follow-up, on-failure follow-up)
(e.g., [1]).
Good luck!
g.
[0]
https://searchfox.org/mozilla-central/rev/ea63a0888d406fae720cf24f4727d87569a8cab5/xpcom/threads/MozPromise.h#98
[1]
https://searchfox.org/mozilla-central/rev/ea63a0888d406fae720cf24f4727d87569a8cab5/dom/media/ChannelMediaDecoder.cpp#392
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