Question

I’m writing a graphical application using Objective-C for the front end and C++ for the graphics processing and network communication. I read around on Apple’s site looking for a way to link either a .dylib or .so with my C++ code in it to my Xcode project, but nothing seemed to work. I was able to get the project to reference it and link against it, but when I tried to call functions from that .dylib, it was saying that it didn’t know what I was trying to do. Does anyone know what is going on here?

I know that Objective-C has all the libraries I would need to do graphics and networking, but I just feel like doing it like this. I haven’t done much C++ in a while and I want to learn more Objective-C, so what better way than to use them together?

Thanks,
Robbie

Answer 1

You’re going to hit one obstacle in the form of what’s called “name mangling”. C++ stores function names in a way not compatible with Obj-C.

Objective-C doesn’t implement classes in the same way as C++, so it’s not going to like it.

One way around this is to implement a set of simple C functions which call the C++ functions. It’ll be a good challenge to keep the number of C functions as low as possible! You’ll end up with a nice compact interface! 🙂

To declare these functions in a C++ file, you’ll need to mark them as C with:

extern "C" int function_name(char *blob,int number, double foo) {...}

This disables the standard name-mangling.

Build a header file with the prototypes for all these functions that you can share with your objective C code.

You won’t be able to pass classes around in the same way (because your ObjC code can’t use them), but you’ll be able to pass pointers (although you might have to lie about the types a little).