NSString -> std::string
NSString *str = @"aaaaaa";
std::string *string = new std::string([str UTF8String]);
std::string -> NSString
[NSString stringWithCString:str.c_str() encoding:[NSString defaultCStringEncoding]];
NSString *str = @"aaaaaa";
std::string *string = new std::string([str UTF8String]);
[NSString stringWithCString:str.c_str() encoding:[NSString defaultCStringEncoding]];