Re: Using C++ classes from Objective C
Re: Using C++ classes from Objective C
- Subject: Re: Using C++ classes from Objective C
- From: Christopher Nebel <email@hidden>
- Date: Thu, 20 Mar 2008 11:33:51 -0700
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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