App Designer basics: How can I call a function from within a callback

I am trying to find a really simple guide as I am 100% new to creating GUIs in MATLAB. This must be in the documentation but I don't know what to look for or where to start, so apologies.

I have written some functions in MATLAB which I would like to adapt for use in a GUI, but for various reasons I would like to keep the functions within the GUI code rather than call them from an external file (unless this is the only way to do it!). The functions themselves are not important as it's the basics I am getting stuck on.

I would like to be able to call a function from within a callback - i.e. I press a button, a function is called, and then the results of that function are returned to the callback. I created the simple GUI and the callback, and I added a simple function, all through the "code browser".

classdef graphs1 < matlab.apps.AppBase

    % Properties that correspond to app components
    properties (Access = public)
        UIFigure                       matlab.ui.Figure
        FilenameEditFieldLabel         matlab.ui.control.Label
        FilenameEditField              matlab.ui.control.EditField
        ReadButton                     matlab.ui.control.Button
        ThisfilecontainsTextAreaLabel  matlab.ui.control.Label
        ThisfilecontainsTextArea       matlab.ui.control.TextArea
    end
    
    methods (Access = private)
        
        function[test]=square_this(number)
          test=number * number;
        end
    
    end

    % Callbacks that handle component events
    methods (Access = private)

        % Button pushed function: ReadButton
        function ReadButtonPushed(app, event)
            
            test_value=square_this(12)
            app.ThisfilecontainsTextArea.Value = num2str(test_value);


        end
    end

When I run the GUI I get the error message "Undefined function 'square_this' for input arguments of type 'double'.".

To me it is as if the callback cannot see the function at all - so I assume there must be a basic step I am missing.

I learn best through examples, so I have tried searching for "calling functions from within a callback" but I am having trouble finding the help I need.

Thank you.

[Rik]

Where is that function located? Is it on the path, or only in the current folder?

[Paul Richardson]

It's further up in the same code, thank you for looking

[Rik]

Can you attach the code using the paperclip icon? I don't currently have any ideas about why this error would occur.

[Paul Richardson]

Thank you, i have attached the mlapp file.

Answer 1

[Paul Richardson]

OK so maybe bad form to answer one's own question but after doing some digging and finding an example elsewhere, it turns out that all it needs is to also pass the "app" object into the function (even though it is not explicitly used by the function). The code below now works in that mlapp file:

    
    methods (Access = private)
        
        function[test]=square_this(app,number)
          test = number * number;
        end
    
   end
    

    % Callbacks that handle component events
    methods (Access = private)

        % Button pushed function: ReadButton
        function ReadButtonPushed(app, event)
            
            test_value=square_this(app,12)
            app.ThisfilecontainsTextArea.Value = num2str(test_value);


        end
   end

[Francesco Bernardini]

Thank you so much, you saved me a lot of time