On Mar 20, 2008, at 10:32 AM, Rob Napier wrote:

Say you have a C++ object called MyObject in the namespace myapp that you want to access through your ObjC. What I tend to do is create an ObjC++ object called MyObjectWrapper that owns a myapp::MyObject and presents a pure ObjC interface to its methods. Users of MyObjectWrapper don't have to include MyObject.h. The trick is that you need to use void* rather than a real class type in MyObjectWrapper.h like this:

typedef void* MyObjectPtr

@interterface MyObjectWrapper : NSObject
{
  MyObjectPtr myObject;
}

That will get you around having C++ class definitions in your header.

Actually, you don't need the "void" typedef -- you can exploit the fact that "class" and "struct" are (almost) synonymous in C++:

        struct MyObject; // forward declaration.
        typedef struct MyObject MyObject; // this is Objective-C, after all...

        @interterface MyObjectWrapper : NSObject
        {
                MyObject *myObject;
        }

Compiles fine in Objective-C or Objective-C++. In your implementation, you give the real definition of MyObject:

        class MyObject {
                ...
        };

C++ (or at least gcc) doesn't mind that it was forward-declared using "struct", since the only difference between "class" and "struct" is the default access privilege.


--Chris N.
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