Getting variables from a custom function with a GUI

I've written a function that creates a GUI requesting the user to input two dates (start and stop). I've included format checking to ensure the user has inputted things correctly.

The part I am missing is how to assign the variables in a way to allows the inputs to be accessible outside the function (i.e. when calling the function with a different script).

Any advice would be appreciated. I can repost sharing the code if that would help.

[Charlie Wood]

Thank you all for the advice. The function is now performing as desired with uiwait. I've included the final version which also includes format verfication using try/catch that ensures the GUI does not close until the dates are provided correctly.

function [startDate, stopDate] = dateInputGUI()

% Set default start and stop dates

defaultStartDate = datestr(datetime('today'), 'dd mmm yyyy HH:MM:SS.FFF');

defaultStopDate = datestr(datetime('tomorrow'), 'dd mmm yyyy HH:MM:SS.FFF');

% Create figure and components

f = figure('Position', [400, 400, 400, 220], 'Name', 'Date Input');

uicontrol('Style','text','String','Expected format: dd mmm yyyy HH:MM:SS.FFF','Position',[50,180,260,20]);

uicontrol('Style', 'text', 'String', 'Start Date:', 'Position', [50, 140, 70, 20]);

startDateEdit = uicontrol('Style', 'edit', 'Position', [130, 140, 220, 20],'String',defaultStartDate);

uicontrol('Style', 'text', 'String', 'Stop Date:', 'Position', [50, 100, 70, 20]);

stopDateEdit = uicontrol('Style', 'edit', 'Position', [130, 100, 220, 20],'String',defaultStopDate);

uicontrol('Style', 'pushbutton', 'String', 'Submit', 'Position', [110, 50, 80, 30], 'Callback', @submitCallback);

% wait until the figure is deleted

uiwait(f);

% Callback function for submit button

function submitCallback(~,~)

startDate = get(startDateEdit, 'String');

stopDate = get(stopDateEdit, 'String');

%Convert to datetime to confirm string is in the correct format and

%that the dates are in order.

try

startDateObj = datetime(startDate, 'InputFormat', 'dd MMM yyyy HH:mm:ss.SSS');

stopDateObj = datetime(stopDate, 'InputFormat', 'dd MMM yyyy HH:mm:ss.SSS');

% Check if start date is before stop date

if startDateObj < stopDateObj

disp('Dates are valid and start date is before stop date.');

delete(f);

else

disp('Error: Start date should be before stop date.');

end

catch

disp('Error: Invalid date format. Please use "dd mmm yyyy HH:MM:SS.FFF".')

end

end

end

[Stephen23]

Note that DATESTR is deprecated, will be removed in the future, and is NOT recommended.

Replace:

datestr(datetime('today'), 'dd mmm yyyy HH:MM:SS.FFF')

ans = '10 Jan 2024 00:00:00.000'

with e.g.:

string(datetime('today', 'Format','dd MMM yyyy HH:mm:ss.SSS'))

ans = "10 Jan 2024 00:00:00.000"

[Charlie Wood]

Thanks for the recommendation @Stephen23. I've made the changes.

Answer 1

[Voss]

Use uiwait to pause execution of the code, in this case pause until the figure is deleted, and delete the figure in the submit button callback.

function [startDate, stopDate] = dateInputGUI()

    % initialize startDate and stopDate in case the user closes the figure 
    % without clicking the submit button. these variables need to be 
    % defined in order to be output. (you could also initialize them to 
    % defaultStartDate and defaultStopDate or something else, depending on 
    % what you want the outputs to be when the user closes without clicking
    % submit.)
    startDate = '';
    stopDate = '';

    % Set default start and stop dates
    defaultStartDate = datestr(datetime('today'), 'dd mmm yyyy HH:MM:SS.FFF');
    defaultStopDate = datestr(datetime('tomorrow'), 'dd mmm yyyy HH:MM:SS.FFF');
    
    % Create figure and components
    f = figure('Position', [400, 400, 400, 220], 'Name', 'Date Input', 'Menubar','none','NumberTitle','off');
    uicontrol('Style','text','String','Expected format: dd mmm yyyy HH:MM:SS.FFF','Position',[50,180,300,20]);
    uicontrol('Style', 'text', 'String', 'Start Date:', 'Position', [50, 140, 70, 20]);
    startDateEdit = uicontrol('Style', 'edit', 'Position', [130, 140, 220, 20],'String',defaultStartDate);
    uicontrol('Style', 'text', 'String', 'Stop Date:', 'Position', [50, 100, 70, 20]);
    stopDateEdit = uicontrol('Style', 'edit', 'Position', [130, 100, 220, 20],'String',defaultStopDate);
    uicontrol('Style', 'pushbutton', 'String', 'Submit', 'Position', [110, 50, 80, 30], 'Callback', @submitCallback);
    
    % wait until the figure is deleted or uiresume(f) is called:
    uiwait(f);
    
    
    % Callback function for submit button
    function submitCallback(~, ~)
        startDate = get(startDateEdit, 'String');
        stopDate = get(stopDateEdit, 'String');
        % delete the figure:
        delete(f);
    end

end

[Charlie Wood]

Thank you.

[Voss]

You're welcome!

Answer 2

[Sonesson]

Hello Charlie,

There are a couple of methods to accsess variables outside of their local function workspace.

The most straightforward is to simply define them as an output variable for the function

%% Script that calls the function handling the user input
[StartDate,StopDate] = FunctionThatGetsUserInputThroughGUI(SomeInput)
%StartDate and StopDate is now available in the workspace that called the
%function.

%Assume you have some function to handle the variables
%Define the output variables as [output1, output2,..., outputN]
function [StartDate, StopDate] = FunctionThatGetsUserInputThroughGUI(SomeInput)
% your code here that creates GUI resulting in the start and stopdate e.g.
StartDate = datetime('yesterday');
StopDate  = datetime('today');
end

Less reccommended options would be to use assignin...

%% Script that calls the function handling the user input
FunctionWithAssignin(SomeInput)
%StartDate and StopDate is now available in the workspace that called the
%function.

function FunctionWithAssignin(SomeInput)
% your code here that creates GUI resulting in the start and stopdate e.g.
StartDate = datetime('yesterday');
StopDate  = datetime('today');

assignin('caller','StartDate',StartDate)
assignin('caller','StartDate',StartDate)
end

... or global variables

%% Script that calls the function handling the user input
global StartDate StopDate

FunctionWithGlobals(SomeInput)
%StartDate and StopDate is now available in the workspace that called the
%function.

function FunctionWithGlobals(SomeInput)
global StartDate StopDate
% your code here that creates GUI resulting in the start and stopdate e.g.
StartDate = datetime('yesterday');
StopDate  = datetime('today');
end

Good Luck!

[Charlie Wood]

Thank you for the response. I am using the first recommended method. I believe my issue is in the GUI functionality itself. My intent is to provide an easy way for the user to input a date and click a submit button. Issue is it seems things move forward without waiting for the user to click "Submit". I'm still new to functions and GUI usage so any advice is appreciated.

function [startDate, stopDate] = dateInputGUI()

% Set default start and stop dates

defaultStartDate = datestr(datetime('today'), 'dd mmm yyyy HH:MM:SS.FFF');

defaultStopDate = datestr(datetime('tomorrow'), 'dd mmm yyyy HH:MM:SS.FFF');

% Create figure and components

f = figure('Position', [400, 400, 400, 220], 'Name', 'Date Input');

uicontrol('Style','text','String','Expected format: dd mmm yyyy HH:MM:SS.FFF','Position',[50,180,260,20]);

uicontrol('Style', 'text', 'String', 'Start Date:', 'Position', [50, 140, 70, 20]);

startDateEdit = uicontrol('Style', 'edit', 'Position', [130, 140, 220, 20],'String',defaultStartDate);

uicontrol('Style', 'text', 'String', 'Stop Date:', 'Position', [50, 100, 70, 20]);

stopDateEdit = uicontrol('Style', 'edit', 'Position', [130, 100, 220, 20],'String',defaultStopDate);

uicontrol('Style', 'pushbutton', 'String', 'Submit', 'Position', [110, 50, 80, 30], 'Callback', @submitCallback);

% Callback function for submit button

function submitCallback(~, ~)

startDate = get(startDateEdit, 'String');

stopDate = get(stopDateEdit, 'String');

end

end

[Stephen23]

Use WAITFOR or UIWAIT.