MATLAB: Returning variables from programmatic GUIs - matlab

Question

I have been trying to program a GUI which is supposed to receive one variable as an input and perform several operations that generate another variable.
The GUI will have one pushbutton that closes the GUI.
I am not (and don't want) to use GUIDE.
Below, I provide a minimal working example of a GUI that simply adds one to the input variable. The "Done" push button closes the GUI but I cannot find out a way to export the variable to the workspace.
% Is this the correct way to initialize the function for what I am trying to do?
function outputVariable = exampleGUI(inputVariable)
% Initialize main figure
hdl.mainfig = figure();
% Add Button
hdl.addPushButton = uicontrol(hdl.mainfig, 'Units', 'normalized',
'Position', [0.05 0.6 0.3 0.25], 'String',
'Add One', 'Callback', #addOne);
% Done Button
hdl.donePushButton = uicontrol(hdl.mainfig, 'Units', 'normalized',
'Position', [0.65 0.6 0.3 0.25], 'String',
'Done', 'Callback', #done);
% Static text
hdl.sliceNoText = uicontrol(hdl.mainfig, 'Style', 'text',
'Fontsize', 16, 'Units', 'normalized',
'Position', [0.35 0.2 0.3 0.25]);
function addOne(~, ~, ~)
inputVariable = inputVariable + 1; % add one to the current inputVariable
set(hdl.sliceNoText, 'String', num2str(inputVariable)); % change static text
newVariable = inputVariable; % new variable to be exported
end
function done(~, ~, ~)
delete(hdl.mainfig); % close GUI
end
end
I would like to do something like:
In the workspace:
outputVariable = exampleGUI(inputVariable)
And after adding one to the input variable a certain number of times, I would push the "Done" pushbutton and the GUI would be closed and the workspace would contain both inputVariable and the outputVariable.
Thanks a lot.
fnery

Answer 1

This is an example of what you can do. There are a ton of things you can do to make this work with the functionality you want. Typically I don't like to have any variables in the whole function's workspace besides the inputs and outputs as well as the guihandles. I use setappdata and getappdata to store other variables and have them accessible to callbacks. This is up to you, but the following is an example of how you can make your simple gui work. The CloseRequestFcn allows you the handle what happens if the user just closes the gui. Hope this helps. In addition, the waitfor prevents the function from returning until the function is closed. If you want, you can also set the figure's 'WindowStyle' property to 'modal' to force the user to put an input before he can close the gui.
function outputVariable = exampleGUI(inputVariable)
% Any variables declared here will be accessible to the callbacks
% Initialize output
outputVariable = [];
% Initialize newVariable
newVariable = [];
% Initialize main figure
hdl.mainfig = figure('CloseRequestFcn',#closefunction);
% Add Button
hdl.addPushButton = uicontrol(hdl.mainfig, 'Units', 'normalized', 'Position',[0.05 0.6 0.3 0.25], 'String', 'Add One', 'Callback', #addOne);
% Done Button
hdl.donePushButton = uicontrol(hdl.mainfig, 'Units', 'normalized', 'Position',[0.65 0.6 0.3 0.25], 'String', 'Done', 'Callback', #done);
% Static text
hdl.sliceNoText = uicontrol(hdl.mainfig,'Style','text','Fontsize',16,'Units','normalized','Position',[0.35 0.2 0.3 0.25]);
function addOne(hObject,eventdata)
inputVariable = inputVariable+1; % add one to the current inputVariable
set(hdl.sliceNoText, 'String', num2str(inputVariable)); % change static text
newVariable = inputVariable; % new variable to be exported
end
function closefunction(hObject,eventdata)
% This callback is executed if the user closes the gui
% Assign Output
outputVariable = newVariable;
% Close figure
delete(hdl.mainfig); % close GUI
end
function done(hObject,eventdata)
% Assign Output
outputVariable = newVariable;
% Close figure
delete(hdl.mainfig); % close GUI
end
% Pause until figure is closed ---------------------------------------%
waitfor(hdl.mainfig);
end