[Development] QMetaType support for QFuture

Sona Kurazyan sona.kurazyan at qt.io
Fri May 7 17:11:05 CEST 2021

Hi Arno, 

You could use the QFutureInterfaceBase (non-templated) class directly to build a type-erased future, that's basically what QFuture is using underneath. Although it's internal (not documented and is considered to be private), but it's declared in a public header (qfutureinterface.h) and you can still use it. QFutureInterfaceBase's methods for accessing its internals are public (with a few exceptions that you probably won't need to use). 
I hope that helps.

Best regards,

> -----Original Message-----
> From: Development <development-bounces at qt-project.org> On Behalf Of
> Arno Rehn
> Sent: Friday, May 7, 2021 4:07 PM
> To: Qt development mailing list <development at qt-project.org>
> Subject: [Development] QMetaType support for QFuture
> Hey everyone,
> I'm currently working on making QFuture return types work transparently in
> QtWebChannel. For remote clients, method return values are received
> asynchronously via callbacks anyway.
> However, QFuture introspection is not supported by the meta-type (yet) and
> there's no other way to register a generic QVariant-based continuation for
> "any" QFuture. All implementation details are private or protected and only
> some friend classes have access.
> I was wondering if I should add a local "workaround" to QWebChannel only
> (like QWebChannel::registerFutureType<int>() to support QFuture<int>) or
> if I should push something more general to QtCore. Maybe just some
> additional private API that supports the necessary private member access?
> Looking forward to some feedback.
> Regards,
> Arno
> --
> Arno Rehn
> Tel +49 89 189 166 0
> Fax +49 89 189 166 111
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