Struct Object definition in Simulink User Defined Functions and Preallocation of Struct Objects

Hello,

My overall goal is to read images into simulink at a fixed rate. These images are being captured by third party software in real time and saved in a folder. It is Simulink's task to read the latest image and do computations on it. I am currently using the user-defined Matlab function block in Simulink to do the task.

I have tried various things, but I am having a hard time wrapping my head around the struct and extrinsic commands. I understand that you have to predefine the struct variables for the memory allocation. And I understand that when you run a function in extrinsic mode, the output is an mxArray. What I don't really get is how to convert the mxArray to the struct object and how to properly use it.

The code below gives me an error of: "Size mismatch for MATLAB expression 'struct.name'. Expected = 1x4 Actual = 1x14 Block MATLAB Function (#24) While executing: none ". Which essentially means that the struct command assigns the string "char" to the "name" field.

What is the proper way of preallocating a struct object, or converting it from mxArray to struct? Also, will there be issues with the varying size of the 'name' entry when during preallocation?

if true
  % code
function y = read_Image() %#codegenn 
coder.extrinsic('imread');
coder.extrinsic('dir');
coder.extrinsic('pause')
dirinfo=struct('name','char','date','char','bytes',double,'isdir','logical','datenum','double' );
dirinfo=(dir('testfolder\\*.png'));
y=(zeros(267,327,3,'uint8'));
y = imread(['testfolder\\',dirinfo(end).name]);
pause(0.25)
end

Cheers,