C++调用Object-C的方法

[ken_scott]

#include <Cocoa/Cocoa.h>
#include <cstdio>
#include <string>
#include <list>

static bool select_folder(std::string & foldername)
{
    foldername.clear();
    NSWindow * window = [NSWindow alloc];
    NSOpenPanel * panel = [NSOpenPanel openPanel];
    [panel setCanChooseFiles:NO];
    [panel setCanChooseDirectories:YES];
    [panel setAllowsMultipleSelection:NO];
//  [panel setMessage:@"Import one or more files or directories."];
    [panel beginSheetModalForWindow:window completionHandler:^(NSInteger result) {
        if (result == NSFileHandlingPanelOKButton)
        {
            NSURL * selection = panel.URLs[0];
            NSString * path = [selection.path stringByResolvingSymlinksInPath];
            foldername = [path cStringUsingEncoding : NSUTF8StringEncoding];
        }
    }];
    return(!foldername.empty());
}

static bool select_files(std::list<std::string> & filename_list)
{
    filename_list.clear();
    NSWindow * window = [NSWindow alloc];
    NSOpenPanel * panel = [NSOpenPanel openPanel];
    [panel setCanChooseFiles:YES];
    [panel setCanChooseDirectories:NO];
    [panel setAllowsMultipleSelection:YES];
//  [panel setMessage:@"Import one or more files or directories."];
    [panel beginSheetModalForWindow:window completionHandler:^(NSInteger result) {
        if (result == NSFileHandlingPanelOKButton)
        {
            for (int index = 0; index < panel.URLs.count; ++index)
            {
                NSURL * selection = panel.URLs[0];
                NSString * path = [selection.path stringByResolvingSymlinksInPath];
                std::string pathname = [path cStringUsingEncoding : NSUTF8StringEncoding];
                filename_list.push_back(pathname);
            }
        }
    }];
    return(!filename_list.empty());
}

int main(int argc, char * argv[])
{
    std::string foldername;
    select_folder(foldername);
    printf("folder: <%s>\n", foldername.c_str());

    std::list<std::string> filename_list;
    select_files(filename_list);
	printf("filelist:\n");
    for (std::list<std::string>::const_iterator iter = filename_list.begin(); filename_list.end() != iter; ++iter)
    {
        printf("    <%s>\n", iter->c_str());
    }
    return(0);
}

C++直接调用Object-C的库的方法，保存为.mm文件，但是编译不过