Hi Afaq,
There are some limitations to using variables in MATLAB function block as opposed to the way it would run in a MATLAB environment. These restrictions are likely imposed to allow effiecient C code generation.
One of the restrictions is that you cannot add fields to the struct on the go. Please read about other restrictions while using struct in MATLAB function block here: https://www.mathworks.com/help/simulink/ug/how-working-with-structures-is-different-for-code-generation.html
You can create a struct with all the fields and assign it to zero at the beginning and then go about assigning the fields.
function a = b(t)
struct = struct('f1', 0, 'f2', 1);
struct.f1=t;
a=struct.f2;
end
If you need to add fields to the struct, please refer to using Variable-sized block variables: https://www.mathworks.com/help/simulink/ug/declare-variable-size-inputs-and-outputs.html
I hope that helps!
