breaking for loop on callback execution

Original question (my own bad-coding-practice-but-super-simple solution below in the accepted answer):

Hello, I have the following code inside of a for loop:

f = figure();
done_button = uicontrol('Parent',f,'Style','pushbutton',...
  'String','Save and quit','Units','normalized','Position',...
  [.915 .92 .07 .03],'Visible','on', 'Callback', @quit);
if done_button.UserData
break
end

and this code for the button callback:

function quit(button, event)
button.UserData = 1;
drawnow
end

The idea is that I want to quit out of the loop when the done button is pressed, but the if statement does not work on button press. I think that's because at the time of the if statement evaluation I have not yet pressed the button, but I don't know how to fix that. I don't want to press this button every loop; only when I want to stop iterating. I looked at this and I'm not sure it applies as I'm not using GUIDE. Would really appreciate help.

[Voss]

Note that the check for the value of done_button.UserData is done immediately after done_button is created. Since no UserData is specified in the command that creates done_button, the UserData will always be empty at that point.

[Vasilisa Iatckova]

I understand that part; I don't understand how to fix that - how do I evaluate done_button.UserData before I close the figure?

[Voss]

I would have to see more of your code, particularly the loop the figure and uicontrol are created in. If I have that information, I can probably advise.

[Vasilisa Iatckova]

Quick follow up for beginners who are struggling through this as well: I found that replacing data in axes for sequential sets of data (in my research, it's brain imaging runs) is better than remaking figures. It will also allow using others' solutions for the problem.

Answer 1

[Vasilisa Iatckova]

To solve my problem, I went with using a text document for sharing variables across functions for now (I create it on button click and check inside the for loop for existance, breaking if exists). That works as intended. With some cleanup (e.g., clear text file before the for loop), it's just a doc with a funny name that's not likely to overwrite any other doc in the working directory. This logic can be used in general to share variables across callbacks and functions.

I'm posting this as the accepted answer because it's a straigtforward 3 x one-liner move, with light computation, doesn't require any FEX solutions, and will work for beginners like myself when all else that was tried fails. Here's example code:

% inside main function:
fid = fopen('I_am_done_for_now.txt', 'w'); fclose(fid); % first pass & clean up after the last button press
for i = 1:1000 % or your range of stuff
    if isempty(load('I_am_done_for_now.txt')) % do next iteration if file is empty (button hasn't been clicked)
        f = figure(); % with some window callbacks
        plot(rand([100, 1])) % or your useful data to look at
        done_button = uicontrol('Parent',f,'Style','pushbutton',...
          'String','Quit','Units','normalized','Position',...
          [.915 .92 .07 .03],'Visible','on', 'Callback', @quit); % or any other callback like a key press
    else
        break
    end
end

% callback
function quit(button, ~)
f = fopen('I_am_done_for_now.txt', 'w');
fprintf(f, '1'); % or anything else
fclose(f);
delete(button.Parent) % closes figure
end

Answer 2

[Walter Roberson]

f = figure();
done_button = uicontrol('Parent',h,'Style','pushbutton',...
  'String','Save and quit','Units','normalized','Position',...
  [.915 .92 .07 .03],'Visible','on', 'Callback', @quit, ...
  'UserData', 0);

while ~done_button.UserData
  stuff
end

[Vasilisa Iatckova]

Thank you! What I want to do during while ~done_button.UserData is keep executing other callbacks in the figure (I have a moving line and solid lines that appear on key presses + some more), and I don't know how to explicitly restrict that to be inside of the while loop. If you're suggesting that I replace my for loop with a while loop, that won't work because I create and close a figure every iteration (the button will be deleted when figure is closed and it will never be clicked until the user is about to close the figure). The loop ends with waitfor(f) to go to the next iteration.