Accessing c++ class from Obj-C .h file

Nibbie

Posts: 4
Joined: 2009.06

Post: #1

Jun 30, 2009 — 09:59 PM

Hello. I am new here, and just started learning Obj-C. I do have a lot of experience programming in C++ and C# though. Now the problem I am facing is that I want to write most of my classes in C++ rather Obj-C and use them inside Obj-C. I have found alot of information on ths matter and in most cases one just includes "cppclass.h" inside a ".mm" file and and just uses the class. This works just fine as ".mm" compiles nicely as Obj-C++, however when one has class definition and class body in seperate files as in ".h" and ".mm" it becomes harder to use C++ class, as inclusion of "cppclass.h" inside "objc.h" results in the following error:

"error:expected '=', ',',';','asm' or '__attribute__' before 'GoaEngine'

now including "cppclass.h" streight inside ".mm" file compiles just fine. So how do I use C++ class inside a complex Obj-C++ class that is broken into ".h" and ".mm"?

Here is a code snippets just in case if I've done something stupid:

cppclass.h

Code:

#ifndef FOO_H_INCLUDED

#define FOO_H_INCLUDED

class CppClass

    {

    public:

        void setId(int newId);

        int getId();

    private:

        int myId;

    };

#endif // FOO_H_INCLUDED

cppclass.cpp

Code:

#include "cppclass.h"

void CppClass::setId(int newId)

{

    myId = newId;

}

int CppClass::getId()

{

    return myId;

}

Now I have EAGLView.h and EAGLView.m (which I renamed to .mm") created by OpenGL ES Template for iPhone SDK. Just writing #include "cppclass.h" inside EAGLView.h brings up an error. =(

So how do I use C++ class inside Obj-C ?

Oddity007

Member

Posts: 226
Joined: 2008.08

Post: #2

Jul 1, 2009 — 05:50 AM

From what I know of, .mm is the only option. Problem is that with c++ everything gets compiled as c++.

You could try:

Code:

//c++ File

class MyClass{int x;} A;

//c header

typedef struct {int x;}MyClassAlias;

extern MyClassAlias A;

Of course this means no methods.

DoG

Moderator

Posts: 869
Joined: 2003.01

Post: #3

Jul 1, 2009 — 01:53 PM

All ObjC modules that use C++ headers need to be compiled as ObjC++, aka all modules that include a C++ header must be .mm files.

Don't panic.

dsedov

Nibbie

Posts: 4
Joined: 2009.06

Post: #4

Jul 1, 2009 — 11:07 PM

Yes, I understand about .mm. The problem I'm having is that if I include "cppclass.h" in EAGLView.mm everything works, and I can create instances of that class. Now if I include it in EAGLView.h - it does not compile =(

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