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Can an Obj-C Class Used with C++?

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Can an Obj-C Class Used with C++?

Feb 22nd, 2009

Is there a way for me to use an obj-C class with my C++ program? If so, what special parameters do I have to specify during the compilation phase, and if I needed, changes to my source code files?

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Re: Can an Obj-C Class Used with C++?

Feb 22nd, 2009

there is no such thing as an "obj-c" class. C language knows nothing about classes. Maybe you mean a structure object declared in a c translation unit (*.c program) ?

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
// *.cpp file
extern C int myint;
// *.cpp file
extern C int myint;

if you have a large group of objects

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
// *.cpp file
extern C
{
    int myint;
    // blabla
};
// *.cpp file
extern C
{
    int myint;
    // blabla
};

Last edited by Ancient Dragon; Feb 22nd, 2009 at 10:28 pm.

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Re: Can an Obj-C Class Used with C++?

Feb 23rd, 2009

The question is Objective-C language.
As far as I know, GNU Objective-C++ allows some mix of C++ and Object-C modules (I never used it).
http://en.wikipedia.org/wiki/Objective-C
See also:
http://www.faqs.org/faqs/computer-lang/Objective-C/faq/

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Re: Can an Obj-C Class Used with C++?

Feb 23rd, 2009

What I am guessing is that you dont have the source of of the .obj(or .o) file.
Don't worry. If you know what all prototypes where there in the source file, you can create a header file which have all the prototypes and then compile it. It will compile easily. But when you are linking, be sure to link the object file along the header file and your main source file.
I know its getting bit confusing so heres a brief example.
Lets say the object file contains a structure and a function

someobj.c

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
struct myType
{
int a;
float b;
};
 
int f1(myType x)
{
return( x.a);
}
struct myType
{
int a;
float b;
};

int f1(myType x)
{
return( x.a);
}

But you dont have the code have the code of the above file right? You just have the precompiled obj file( which will be a .o file or a .obj file).

Now I want you to create a new file containing the prototype(not the definition) of all the data structure and function used. In our example this will be:
myobj.h

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 C++ Syntax (Toggle Plain Text) 
struct myType;
int f1(myType);
struct myType;
int f1(myType);

Now just include the myobj.h in your main cpp program
main.cpp

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include<iostream>
#include "myobj.h"
using namespace std;
int main()
{
some code 
return 0;
}
#include<iostream>
#include "myobj.h"
using namespace std;
int main()
{
some code 
return 0;
}

Now compile the main.cpp. In g++ you compile with the compile only flag -c

Help with Code Tags

C++ Syntax (Toggle Plain Text)

g++ -c  main.cpp

And then you link the main.o and the myobj.o together to make your executable

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
g++ -o mainProgram.exe main.o myobj.o
g++ -o mainProgram.exe main.o myobj.o

And you are done;

Note that you can avoid writing the myobj.h by directly declaring the prototype in your main program.

I hope it helps

Also note that your code of the myobj.o i.e myobj.c should not contain any c++ incompatible code. Also, the object file should have been of the same platform as your program(i.e. it should not been that you compiled the .obj file on a Unix and now try to link in a windows box)

Siddhant Sanyam
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