Error using extractfield in app designer

I am attempting to extract the values from specific fields of a structure in app designer.

I first added a private property(app.Mystruct) and a function which loads the struct from a mat file.

properties (Access = private)
        Mystruct % Description
    end
    
    properties (Access = public)
    end
    
    methods (Access = private)
        
        function Start(app)
            Mystruct=load('AccelQuery.mat')
        end
    end

In the call back function I used:

    rmdData=app.Mystruct;
rmdData.SERIAL_NUMBER=extractfield(rmdData,'SERIAL_NUMBER');

In an effort to extract the values from that field('SERIAL_NUMBER').

I then receive this error:

Error using extractfield
Expected input number 1, S, to be one of these types:

struct

Instead its type was double.

Error in extractfield (line 39)
validateattributes(S, {'struct'}, {'vector'}, fcnname, 'S', 1)

Any suggestions to correct this error?

Answer 1

[Matt J]

The error message has told you that rmdData, as fed to extractfield, is not a struct. You should check what it actually is, and how it got that way.

[Alexandra Philip]

I checked rmdData and it is saying that it is a struct.

[Matt J]

Well, attach rmdData in a .mat file so that we can try to reproduce the error.