How to use c++ and objective-c together in XCode 4.2

Question

I had a trouble to combine c++ and objective-c together in developing a iphone app. I had a 3rd party library to use in the app. I had a plan to use c or c++ to wrap the library and then use objective-c to call it. After I had finished the class with c++, I had a trouble to use it in objective-c. Is there any sample code? Thanks.

in the objective-c head file. I write

#import <UIKit/UIKit.h>
#import "ZJTConstants.h"
#include "TTSAdapter.h"

class Adapter;
@interface ZJTVBlogViewController : UIViewController {
@private
    Adapter* adapter;
}
@end

and in the mm file, I write:

if (self) {
    adapter = Adapter::getInstance();
    // Custom initialization
}

Is it write?

Monochromatism

It seems you are indeed using .mm file, so, what's the trouble? you have not told us what problem you are facing. – Toscana

It says that there are some compilation error, so I was wondering if there's anything wrong in the syntax. – Monochromatism

Have you fixed it? If not, just precise what "some compilation error" is. – Toscana

Thanks, it is not fixed yet. But the reason is that a library file in the project do not have i386 version which is needed in the simulator compilation. I was searching for one. – Monochromatism

Answer 1

Calling C++ code from Objective-C code involves ending your file with .mm (instead of .m) so that the Objective-C++ compiler will be used.

This compiler can understand both C++ and Objective-C.

In other words, the ObjC++ compiler lets you put C++ code directly in Objective-C methods, and vice versa.

Take a look at Cocoa_With_Carbon_or_CPP example and Strategies for Using C++ in Objective-C Projects (and vice versa) article .

Adopt

Answer 2

In XCode there is a flag to compile all files as Objective-C++. I've used it to compile huge C++ libraries into iOS programs.

If you look at the "Build Settings" there is a place written "Compile Sources As". There is a dropdown menu there where you can select Objective-C++. In the clang/gcc commandline I think it is "-x objective-c++".

Lieu

Size doesn't matter What you have to do is just change change the extension to .mm of to class that containing C++ code ... – Headmistress

@HikmatKhan What I was suggesting is that sometimes renaming files, especially in big (multiperson) projects is not really an option. – Lieu

@kevlar If you look at the "Build Settings" there is a place written "Compile Sources As". There is a dropdown menu there where you can select Objective-C++. In clang I think it is "-x objective-c++" – Lieu

Answer 3

Just rename your file to have an extension .mm instead of .m.

To mix C++ code with Objective-C code, you will need Objective-C++ compiler. XCode by default compiles .m files with Objective-C compiler and .mm ones with Objective-C++ one.

Toscana