[Development] Circular dependencies for Q_PROPERTY

[Mike Krus]

Hi Simon

yes that worked, didn’t know about Q_MOC_INCLUDE 

Thanks!

PS: seems Creator’s syntax highlighter doesn’t know about it either :) 


> On 27 Apr 2020, at 11:08, Simon Hausmann <Simon.Hausmann at qt.io> wrote:
> 
> Hi,
> 
> I think the solution may involve keeping forward-declarations but adding visibility to the "other" types in moc generated code by using Q_MOC_INCLUDE in A to include B and vice versa. Does that make sense?
> 
> 
> Simon
> From: Development <development-bounces at qt-project.org> on behalf of Mike Krus via Development <development at qt-project.org>
> Sent: Monday, April 27, 2020 11:52
> To: Qt Development Group <development at qt-project.org>
> Subject: [Development] Circular dependencies for Q_PROPERTY
>  
> Hi
> 
> I have 2 classes, A and B, derived from QObject, each have a property
> of type pointer-to-other-class. So
> 
> class A : public QObject {
> Q_PROPERTY(B *foo …)
> …
> };
> 
> And:
> 
> class B : public QObject {
> Q_PROPERTY(A *foo …)
> …
> };
> 
> Because of the circular dependency, I can’t #include the full class
> definition, just do forward declaration.
> 
> Now this fails in Qt 6, seems the moc generated code needs the 
> full class declaration.
> 
> Looking at generated moc code, looks like creating the meta object
> requires a qt_metaTypeArray<A*, bool> which checks that A derives
> from QObject by calling  IsPointerToTypeDerivedFromQObject
> which uses sizeof() which requires the full type.
> 
> Any way around this? Seems like a rather big regression compared
> to Qt 5…
> 
> 
> Mike
> 
> —
> Mike Krus | mike.krus at kdab.com | Senior Software Engineer
> KDAB (UK) Ltd., a KDAB Group company
> Tel: UK Office +44 1625 809908   Mobile +44 7833 491941
> KDAB - The Qt Experts, C++, OpenGL Experts

—
Mike Krus | mike.krus at kdab.com | Senior Software Engineer
KDAB (UK) Ltd., a KDAB Group company
Tel: UK Office +44 1625 809908   Mobile +44 7833 491941
KDAB - The Qt Experts, C++, OpenGL Experts


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