On Jan 31, 2012, at 1:31 PM, Howard Moon wrote:
> How does one call a Cocoa function from C++ code?
>
> I've got an existing .cpp file that leverages the vstgui framework,
> which includes support for Cocoa in the underlying layers. However, vstgui
> does not support dialogs or alerts. My code already supports native Windows
> dialogs/alerts, and Carbon windows/alerts, as needed, and I'd like to add
> support for Cocoa when my audio plug-in is compiled as 64-bit on the Mac.
>
> One of my current functions is something like this:
>
> void MyObj::showAlert( char* text, char* caption )
> {
> #ifdef WIN32
> // calls ShowMessage
> #else
> // calls CreateStandardAlert and RunStandardAlert
> #endif
> }
>
> I'd like to add the ability to support Cocoa, by adding a .mm/.h file
> with the Cocoa code to display an NSAlert, and call it from here when the
> preprocessor symbol MAC_COCOA is defined. I've created the Cocoa files, but
> how can I include and call into that code from my .cpp file? Simply adding
> either #import or #include of my new .h file causes many many errors, even
> though the .mm file itself compiles fine.
>
> Anyone know of a very simple example showing what I need to do here?
> All the examples I find so far show making the call from a .mm file in the
> first place, but I can't do that because my code is also compiled for 32-bit
> Carbon (and Windows). How do I call from a .cpp file into a .mm file?
Put this at the top of your .h file:
#ifdef __cplusplus
extern "C" {
#endif
and this at the bottom:
#ifdef __cplusplus
}
#endif
Then, just wrap all the Cocoa method calls you want to make in plain C
functions, and restrict all usage of Objective-C to the .m, leaving the .h as
plain C.
Charles
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