Traverse cell array of structures of ... in mex

Does anyone have a nice .mex example where we pass in a cell array of struct, and interrogate fields in each structure?

This mex newby is baffled as to why mxIsStruct returns false when the following is passed a cell array of struct:

 void blah(mxArray* X)
 mxArray* pm;
 mwIndex i;
 i = 1;
 pm = mxGetCell(X,i);
 if (~mxIsStruct(pm)) {
    mexErrMsgTxt("Not a structure");
 }

[Kaustubha Govind]

What do you see when you print mxGetClassName(pm)?

Answer 1

[Jan]

You are talking about C, not Matlab. In C the NOT operator is "!", not "~".

if (~mxIsStruct(pm))   % Bad
if (!mxIsStruct(pm))   % Good

The tilde ~ is the bitwise complement in C.

[Peter Cotton]

Clunk. I sentence myself to two weeks debugging other's code.

Answer 2

[Jan]

I've published two different C-Mex function which access cells and struct fields: frmfield and cstrainbp. Perhaps they help.

Answer 3

[Kaustubha Govind]

The example phonebook.c accepts an array of structs and returns a cell array - this should serve as a good starting point.

Answer 4

[James Tursa]

C is 0-based indexing. You have this in your code:

i = 1;

Are you sure you have two elements in X? Or did you mean:

i = 0;