How to fake an app handle in the arguments?

Hello.

I am working on a project which involves an app. What I do is to give the submethods a handle to the app, so that they can use the apps getter and setter methods, as well as the log file. This is done via Argument Validation, aka:

function [] = myFun(I, app, opt)

arguments
        I               (:, :)  uint8               % the image
        app             (1, 1)  eva 
            % Handle back to the app, to transfer data
        opt.whatever1   (1, 1)  {mustBeNumeric} = 100
        opt.whatever2   (1, 1)  {mustBeNumeric} = 100
        opt.debug       (1, 1)  logical         = false
end

% Function code

end

Now what I would like to do, is to be able to call the function like myFun(I, ?, 'debug', true), where I use the debug flag to not go into the parts of the code which actually uses the app handle. This would allow me to call the methods in the command line and not just from inside the app. In this case the '?' stands for whatever can be used. Empty strings or arrays do not work. Naively I'd use something like a Nullpointer, but I don't know if something like that exists in Matlab.

Any ideas or insights would be chuffing tremendous. Or if you know that this won't work as intended, that'd be good to know as well.

Answer 1

[dpb]

Use mustBeScalarOrEmpty validation function instead of fixed size would get past that hurdle. I've no klew whether it'll actually work as intended or not, I've never used any of the argument validation stuff...

[Adrian]

This seems to work.

Additionally I can set

opt.debug   (1, 1)  logical = isempty(app);

which immediately sets the debug flag as intended.

Thank you very much.