Appdesigner TextArea display warning message from function

How do I display warning messages created in a function, outside of the app. Like a feedback system if certain tasks succeed.

For example:

function [data]=somefunction(filename)
if ~isfile(filename)
    warning('File not found')
end
data = readtable(filename);
end

This is called by a buttonpushedfunction

function OpenButtonPushed(app, event)
            [app.data] = initvar();
            app.TextArea.Value =[app.TextArea.Value];%, warning('')];
end

How do I connect the warning message to the value in the TextArea?

The warning message does show in the command window in Matlab.

I have tried adding the link in the warning message in the function, but this did not help.

Thank you in advance.

Answer 1

[Abhipsa]

Hi @Tik Tak,

You can use the “evalc” function in MATLAB to capture all output that would typically be displayed in the command window, including warnings, during the execution of a specified expression. By using this function, you can redirect these outputs to a string variable.

The captured output can then be processed by splitting into individual warning messages based on newlines. This approach effectively captures all warnings generated during the execution of a function.

Here is how the two pieces of code that you have provided can be connected to implement the feedback system:

% I am assuming that the required properties names have been created
%This is a callback function for button in app designer
 function OpenButtonPushed (app, event)
            % Initialize a string to store warning messages
           warnStr = evalc(' somefunction(app, file.csv'');'); %replace ‘file.csv’ with your file name
           
            % You can use a regular expression to clean up non-printable characters (optional step)
            cleanWarnStr = regexprep(warnStr, '[^\x20-\x7E]', '');
            cleanWarnStr = strtrim(cleanWarnStr); % Trim leading/trailing whitespace

            % Split the cleaned string into separate messages
            warningMessages = strsplit(cleanWarnStr, newline);
            warningMessages = warningMessages(~cellfun('isempty', warningMessages)); % Remove empty lines

            % Display all captured warnings in the TextArea
            if ~isempty(warningMessages)
                app.TextArea.Value = [app.TextArea.Value; warningMessages'];
            else
                app.TextArea.Value = [app.TextArea.Value; {'File loaded successfully.'}];
            end
  end

The output of the same in two cases:

1. File found

2. File not found

NOTE: I wanted to display multiple warning messages, so I have added some dummy warnings in the code for the same.

You can use the below MATLAB documentations for further details:

• evalc: https://www.mathworks.com/help/releases/R2021a/matlab/ref/evalc.html
• strsplit: https://www.mathworks.com/help/releases/R2021a/matlab/ref/strsplit.html

I hope this helps!