Update app.textarea inside a parfor loop

I'm trying to update app.TextArea in the app designer using parfor_progress

Error: Valid indices for 'app' are restricted in PARFOR loops.

How would I fix the sliced variable that is 'app' or is it just impossible with parfor and the app designer?

Using Matlab 2017b

Example code below:

 clear;

 clc;

 num_iter=100;

 percent=parfor_progress(num_iter);

 parfor i=1:num_iter

    pause(randi(10));

    percent=parfor_progress;

    app.TextArea.Value={percent};

 end

 parfor_progress(0);

Any help/links for further reading would be helpful.

Thanks

Nick

Answer 1

[Walter Roberson]

If you are using a newer release then I would skip all of that and use parallel.pool.DataQueue and send() and afterEach(); see https://www.mathworks.com/help/distcomp/send.html .

[Nick LaSorte]

Thanks Nick

Answer 2

[Ashadullah Shawon]

i am just expanding the accepted answer for the quick understanding. I have uploaded the full appdesigner code and here is also the functions preview using parallel.pool.DataQueue and send() and afterEach()

     methods (Access = private)
        
        function app= func1(app,data)
             %disp(data);
             
             app.textTextArea.Value = strcat('Function 1----',datestr(now));
             %pause(1);
             app.textTextArea.Value = [app.textTextArea.Value;strcat('Function 1----',datestr(now))];
             
         end
        function app= func2(app,data)
            %disp('Function 2');
            
            app.textTextArea.Value = [app.textTextArea.Value;strcat('Function 2----',datestr(now))];
            %pause(1);
            app.textTextArea.Value = [app.textTextArea.Value;strcat('Function 2----',datestr(now))];
            
        end
       
    end
    

    methods (Access = private)

        % Value changed function: ClickOnButton
        function ClickOnButtonValueChanged(app, event)
            q = parallel.pool.DataQueue;
            r = parallel.pool.DataQueue;
         
            afterEach(q, @app.func1);
            afterEach(r, @app.func2);
            parfor i = 1:2
                if i == 1
                  %func1(app);
                  send(q,i);
                  
                else
                  %func2(app);
                   send(r,i);
                end
            end            
                  
        end

        
    end

[Alexander Babin]

Hi, this didn't work for me: I'm trying to display iteration number each time parfor runs a loop, but it only spits out all messages at once after all of them are compete, not as soon as data.queue receives data it seems

[Alexander Babin]

 function sendMessage(app,data)
   app.ProgressTextArea.Value=[app.ProgressTextArea.Value;data];
 end
 
message = parallel.pool.DataQueue;
afterEach(message, @(msg) sendMessage(app,msg));

parfor iteration=1:N
   ...
   msg = ['Completed iteration # ', num2str(iteration)];
   send(message,msg);
end

[Walter Roberson]

you might need to add a drawnow call