How to code a struct input into the c++ app file for shared library

Input to my function is a structure with fields filename (string type) and fft (double). I have followed the MWStructExample.cpp (phonebook example). Please guide as to how it should be further coded. I doubt the syntaxing is wrong somewhere.

            const char *input[] = {"filename", "fft"};
            mwSize dims[2] = {1, NUMBER_OF_STRUCTS };
            mwArray stru(2,dims, 2, input);
            mwArray filename(m, n, mxDOUBLE_CLASS);
            mwArray fft(1, 1, mxDOUBLE_CLASS);
            stru.Get(input[0],1,1).Set(filename);
            stru.Get(input[1],1,1).Set(fft);