在C ++命令行工具项目中使用Objective-C / C静态库

Question

I've created an Objective-C/C static library which I want to use in separated project which is developed under C++

Here is a code of static library:

Info.h

const char * GetSomeInfo();

Info.m

#import "Info.h"
#import <Foundation/Foundation.h>

@interface Info : NSObject

- (NSString *)someInfo;

@end

@implementation Info

- (NSString *)someInfo
{
    return @"getting some info";
}

@end

const char * GetSomeInfo()
{
    Info *info = [[Info alloc] init];
    return [[info someInfo] UTF8String];
}

Then I added Info.h and Info.a into my main C++ Xcode project which looks like command line tool created in Xcode:

#include <iostream>
#include "Info.h"

int main(int argc, const char * argv[])
{
    const char *someInfo = GetSomeInfo();
    printf("some info: %s", someinfo);
    return 0;
}

I added Info.a into project settings -> link binaries with libraries. Also added -ObjC flag to the project. As result I receive linker errors:

Undefined symbols for architecture x86_64: "GetSomeInfo()", referenced from: _main in main.o ld: symbol(s) not found for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation)

How to fix the problem above?

Answer 1

In Info.h, try wrapping the function prototype GetSomeInfo() in an extern "C" and #ifdef __cplusplus statement (starts with 2 underlines), like this:

#ifdef __cplusplus
extern "C" {
#endif
    const char * GetSomeInfo();
#ifdef __cplusplus
}
#endif