MacResearch

Using the Objective-C++ bridge is very straightforward once you know C++. Apple's half-page documentation here should be enough. I don't know of any 'C++ for the Objective-C programmer' resources, but here's a short paragraph from Wikipedia: link(check the "Philosophical Differences between Objective-C and C++" subsection). A good and free C++ book is Bruce Eckel's Thinking in C++, Volume I:link. The fundamental difference between C++ and Obj-C is the typing used. C++ is statically typed(compile-time typing), like C, and Obj-C is dynamically typed(runtime typing). In general, when I experiment with Objective-C++ I try to keep it simple. For example, I usually have some C++ classes I need to use in a Cocoa application. I create a C++ wrapper object that acts as the interface between the ObjC class and the other C++ classes. So I might have the following setup. This is contrived example, sorry :) .

//Obj-C
@interface FooBar: NSObject {
CPPWrapper *wrap; //this is the pointer to the C++ wrapper object
}

-(void) init;
-(void) doSomething;
@end

//C++
//declaration of CPPWrapper analogous to @interface
class CPPWrapper {
CPPWrapper(int x, int y, int z);
int computesum();
};

//Omitted C++ class definition(analogous to @implementation) for now.

//ObjC
@implementation FooBar
-(void) init {
wrap = new CPPWrapper(2,3,5);
wrap->computesum(); //analogous to [wrap computesum] if
//wrap was a pointer to an ObjC object
//and computesum was an ObjC method.
}

Couple of other things: to translate between Objective-C data types and C++ data types look at their common ancestor: C. So, ints, floats, doubles can be passed between ObjC objects and C++ objects very easily, but what about things like strings? It turns out C++ strings can be converted to C strings using the c_str() instance method, and NSStrings and NSMutableStrings can be converted to C strings using cStringUsingEncoding: There are some caveats with using Objective-C++ and Apple's documentation above details them.

Hope this helps,

Chinmoy

P.S. A long example of Objective-C++ is here
Another great C++ tutorial is here

Hi all,

So I have four C++ articles posted so far(here). I have refreshed my memory on a lot of things by writing these, so this has been beneficial for me, as I hope it is for you. Any comments or questions? What would you like covered in the future? I do plan to put more examples where I have the same concepts in Objective-C and C++ in the same article, as well as providing some more examples of Objective-C++.

Regards,
Chinmoy.

Just for the record, Objective-C is *not* the only way to write user interfaces on the Mac!

I write all my code in FPC, which has good support for Cocoa. Even without such language specific support, it is perfectly possible (but harder) to use Cocoa, up to a point.