Question

I need to use C++ file in my project, it’s called CAXException.hpp, and row in project targets “Compile Sources As” – “According to file type” not Objective-C++. But when it’s compiling it always displays me error error: expected '=', ',', ';', 'asm' or '__attribute__' before 'CAXException'
in code:

class CAXException //<-------error here

{}

Please help me to fix it..

Answer 1

If I understand you correctly, you have a C++ header file (.hpp) that you want to include from Objective-C file. Unfortunately, you can’t do that directly. You’ll have to use a workaround.

The easiest is to change the compilation option of each and every Objective-C file (.m) that include this C++ header file (either directly or indirectly) to be compiled as an Objective-C++ file. This can be done either by renaming the files to .mm extension or by changing the option for the compiler for the file.

If this work for you, this will be the easiest, however Objective-C++ is not a complete superset of Objective-C (as C++ is not a superset of C), and some valid Objective-C is invalid Objective-C++ (if C++ keywords are used as variables names).

If this happens, you’ll have to create an Objective-C wrapper to the class, with an implementation in Objective-C++ that simply delegate to the C++ class. That is create an CAXExceptionWrapper.h Objective-C file, containing something like:

@interface CAXExceptionWrapper {
  @private
    void* _CAXExceptionImpl;
}
- (id)init;
// ...
@end

And an `CAXExceptionWrapper.mm’ Objective-C++ file containing:

@import "CAXException.hpp"
@implementation CAXExceptionWrapper
- (id)init {
    if ((self = [super init])) {
        _CAXException = new CAXExceptionWrapper;
    }
    return self;
}
// ...
@end

And then in your Objective-C files, include the wrapper Objective-C header instead of the C++ header.