How C++ gets struct values from Matlab

Does anybody knows how to get a Matlab struct values(string, matrix, double, bool,...) into c++? There is a example in Matlab "phonebook.c" which shows how to do that.

In this example, the output are direct saved in a Matlab cell with the functions mxCreateCellArray(), mxSetCell() etc.

What I want to do is save the values in two vectors in C++. I tried with mxGetField() and mxGetFieldByNumber() to get the values and push them into a vector. But I can only get the pointer of them with the type mxArray. And I used mexPrintf() to show them in Matlab, it looks like

PS. I don't why, when I wrote a * before the pointer, it's wrong.

Thanks a lot.

[Gummibear]

I found the solution to get the double values. The key point is I have to use the function mxGetPr() to get the pointer of a mxArray. For example, to get the phone number "3386":

mxArray *phoneNum;

phoneNum = mxGetField(prhs[0], 0, "phone"); // 3386

double *number;

number = mxGetPr(phoneNum);

mexPrintf("...%f = ", *number);

BUT there is still a problem, the return value of the mxGetPr() is double, I don't konw how to get the names (string) of the 1. field? Can anyone help?

Thanks

Answer 1

[James Tursa]

Looks like your strings are char type and not the newer string type. So you can try the following:

mxArray *mx;
char *name;
mx = mxGetField( prhs[0], 0, "name" );
if( mx && mxIsChar(mx) ) {
    name = mxArrayToString( mx );
    mexPrintf("name = %s\n",name);
    mxFree(name);
}

Answer 2

[Bruno Luong]

For char array

#include "mex.h"
/* File test.c mex file demo access to a string of s.name
 *
 * >> mex test.c
 * >> s = struct('name','Jordan Robert')
 * >> test(s)
 * */

void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
{
    mxArray *FieldName;
#define MAX_LENGTH 100
    char Cname[MAX_LENGTH];
    int lgt;
    
    if (nrhs<1)
        mexPrintf("need 1 argument\n");
    else
    {
        FieldName = mxGetField(prhs[0], 0, "name");
        if (FieldName)
        {
            lgt =  mxGetN(FieldName);
            lgt++;
            if (lgt <= MAX_LENGTH)
                if (mxGetString(FieldName, Cname, lgt)==0)
                    mexPrintf("name is \"%s\"\n", Cname);
                else mexPrintf("mxGetString fails\n");
            else mexPrintf("Buffer too small\n");
        }
        else mexPrintf("field 'name' not exists\n");
    }
}