writing to different file names using for loop in C++ visual studio

Question

I am trying to write some data to different files for each index. i.e. The file name should change from datafile0.res to datafile99.res depending on the index passed.

I am using visual C++ 2008.

The code is:

void write_data(int index) {

ofstream coutput;

// first i need to convert integer index to string. Not sure if right?

ostringstream temp;
temp<<index;
std::string s = temp.str();
std::string dir = "C:\My_Data\datafile" + s + ".res";
coutput.open(dir);

When i run this code, the following error appears:

error C2664: 'void std::basic_ofstream<_Elem,_Traits>::open(const wchar_t ,std::ios_base::openmode,int)' : cannot convert parameter 1 from 'std::string' to 'const wchar_t *'
1>        with
1>        [
1>            _Elem=char,
1>            _Traits=std::char_traits<char>
1>        ]
1>        No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called.

Please need your help.

Thanks in advance

Answer 1

This has nothing to do with your stated goal, or your concatenation.

std::fstream::open, before C++11, requires a const char*, not an std::string.

So:

coutput.open(dir.c_str());