How to store data from pushbutton within a nested function?

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Hunter Stevenson 2018-5-25

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https://ww2.mathworks.cn/matlabcentral/answers/402590-how-to-store-data-from-pushbutton-within-a-nested-function

评论： Stephen23 2018-5-27

I feel like this is a super easy fix, but I cannot seem to figure out how to store a variable within a nested function...Here is my function so far

data_labels and step_labels are variable length cell arrays, while input_labels is a variable length array of sequential numbers between 1 & 10.

My issue is I can get my pushbutton to correctly output 'vals' via the display, but when I try storing vals outside of the push_call function, I cannot seem to get it to overwrite the zeros array.

function vals = MyGUI2(data_labels,input_labels,step_labels)
num_inputs = max(input_labels) - min(input_labels) +1;
num_steps = max(size(step_labels));
components_index = step_labels;
h.table = uitable('units', 'pixels', 'position',...
    [10, 10, num_inputs*110, num_steps*40],...
    'columnname', data_labels,...
    'columnformat', {'logical'}, 'ColumnEditable', true,...
    'rowname', step_labels,...
    'data', true(numel(components_index),num_inputs));
% Creates a pushbutton to save data
vals = zeros(num_steps,num_inputs);
h.push = uicontrol('style','pushbutton','units','pixels',...
                'position',[num_inputs*200/4,50,80,40],'string','Done',...
                'callback',@push_call);
    function vals = push_call(varargin)
        vals = get(h.table,'data'); % determines which boxes are checked
          disp(vals)  % just displaying your values that you have selected
      end
      % need to strore vals somehow!
end

Thanks in advance :)

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Answer 1

Stephen23 2018-5-25

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/402590-how-to-store-data-from-pushbutton-within-a-nested-function#answer_321963

编辑：Stephen23 2018-5-25

在 MATLAB Online 中打开

Add waitfor right at the end of the main function (the one that you call from the command window). E.g.:

...
waitfor(h.push)
end

Basically your confusion is because functions are synchronous, but GUI's are asynchronous. You cannot call the synchronous function which initiates a GUI and expect it to obtain data from asynchronous triggers that occur randomly in the GUI. You can pause the synchronous code until the asynchronous code is not going to run any more (i.e. the GUI is closed) (which is what waitfor does), or store the data in some persistent memory or something similar.

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Stephen23 2018-5-25

编辑：Stephen23 2018-5-25

在 MATLAB Online 中打开

It works for me: I created an MWE function to test it:

function val = testfun()
val = [];
fgh = figure('Position',[400,400,200,100]);
hnd = uicontrol(fgh,'Style','pushbutton',...
    'Callback',@nestfun,'String','click me');
waitfor(hnd)
    function nestfun(~,~)
        val = 1:3;
    end
end

Then called it from the command line:

>> val = testfun() % Did not click button. Closed figure.
val =
     []
>> val = testfun() % Clicked button (callback runs). Closed figure.
val =
     1     2     3

You can see that by clicking the button the callback was called and clearly changed the value of val in the main function's workspace. In both cases val was simply returned as an output argument from the main function. The figure looks like this:

This is an intuitive, robust, and simple way to merge asynchronous code back into a synchronous script or function. Note that it would be very bad practice to write a GUI that magically accesses variables in the base workspace: the best practice is to load/create variables withing the GUI, work with them inside the GUI callback workspace/s, before saving them or returning them to the base workspace as I showed above.

Hunter Stevenson 2018-5-26

Hey! I got it to work out! I am not entirely sure why, but in my nested function I had vals as the output argument, and it was not storing ‘vals’

I noticed you didn’t have any output arguments for your nested function, so I deleted it and it worked out. Any idea why?

Thanks again for your help!

Stephen23 2018-5-27

"I noticed you didn’t have any output arguments for your nested function, so I deleted it and it worked out. Any idea why?"

What does "it worked out" mean? If you delete the nested function nestfun then my code will throw an error when the callback is triggered. Callback functions do not use output arguments.

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