Hi Johannes,
Actually I don't think using braced initialization format ever worked, due
to the C++ standard's unfortunate decision that elements of an
std::initializer_list should be const. My example code there is erroneous.
What you actually need to do is something like:
auto builder = kj::heapArrayBuilder<kj::Promise<void>>(2);
builder.add(kj::mv(promise1));
builder.add(kj::mv(promise2));
auto joined = kj::joinPromises(builder.finish());
-Kenton
On Fri, Sep 8, 2017 at 2:20 AM, Johannes Zeppenfeld <[email protected]>
wrote:
> Hi Kenton,
>
> in [1] you give an example of joining two Promise<void>s to produce a
> Promise<void> that is fulfilled when both other promises have fulfilled (to
> chain a list of related promises, avoiding a TaskSet and allowing to wait
> on the result).
>
> In Capnp 6.0.1 using g++ 5.4.0 this gives me the following error:
>
> error: no matching function for call to ‘joinPromises(<brace-enclosed
> initializer list>)’
> tasks = kj::joinPromises({kj::mv(tasks), kj::mv(newTask)});
>
> /usr/local/include/kj/async.h:312:24: note: candidate: kj::Promise<void>
> kj::joinPromises(kj::Array<kj::Promise<void> >&&)
> friend Promise<void> joinPromises(Array<Promise<void>>&& promises);
> ^
> /usr/local/include/kj/async.h:312:24: note: no known conversion for
> argument 1 from ‘<brace-enclosed initializer list>’ to
> ‘kj::Array<kj::Promise<void> >&&’
>
> Has something changed here to make this no longer possible? Do I have to
> use an ArrayBuilder? Is there some other way to join Promise<void>s without
> needing to allocate an Array?
>
> Thanks!
> Johannes
>
>
> [1] https://github.com/capnproto/capnproto/issues/286#
> issuecomment-185975985
>
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