> Le 7 sept. 2018 à 19:46, Casey McDermott <supp...@turtlesoft.com> a écrit :
>
> We need to link some of our C++ classes to a matching Cocoa class.
> It's easy for Cocoa to reference C++ objects. Going the other way is harder.
>
> We have been using a linker class that has a void pointer to the Obj-C object
> in the C++ header. We then cast it to a Cocoa object in the Obj-C++ source.
> For example, in the C++ header we have:
>
How are you setting the pointer ? If you are using ARC and want to get a strong
reference on the object, you have to use __bridge_retained, which tell ARC to
keep the reference valid.
Once you are done with the objc object, you have to release it.
> void *mCocoaPopupPtr = nil;
>
> Then in the source:
>
> void GSCocoaPopupLinker::setCocoaFieldVisible(const BOOL inValue)
> {
> if (mCocoaPopupPtr != nil)
> {
> GSPopupButton *cocoaPopup = (__bridge GSPopupButton
> *)mCocoaPopupPtr;
> [cocoaPopup setHidden : !inValue];
> }
> }
>
> Problem is, with ARC turned on, the pointer is never nil, so it crashes.
> The void pointer somehow becomes an NSAtom instead of 0.
>
> There's very little documentation on NSAtom, but it appears to be Apple's way
> to
> use the excess bits in a 64-bit address to store class info.
>
> Is there some other way to test for an invalid void pointer?
>
> Thanks,
>
> Casey McDermott
> TurtleSoft.com
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