Unable to assign function handle to variable in specified workspace in app App Designer

Hi, the issue is about Carrying over variables in app-designer to another function.

The idea is to call (STEP ONE) a figure that designed in app designer from an external function (i,e,TestFunc). The Figure equip with a push button . A new routine is execute whenever the push button is press (STEP TWO). For simplicity, the new routine responsible to assign (STEP THREE) the myVar with a value of 5. Ultimately, I want to assigns (STEP FOUR) the function handle myVar into the workspace of TestFunc using the assign in command. Once succesfully carrying the variable into the caller workspace, the fig will be deleted (STEP FIVE). Then, the NewVar will be assigned (STEP SIX) to equal to NewVar, at the TestFunc environment.

To achieve the following objective, the syntax for the TestFunc and fig of the app designer are;

Syntax of TestFunc

function  TestFunc()
%% STEP ONE
fig=app1; % app1 is the name of the figure designed with app designer. With the extension of mlapp
waitfor(fig)

%% STEP SIX
NewVar=myVar;
end

Syntax of fig of the app designer

        function ButtonPushed(app, event)
            %% STEO TWO
            %% Whenever, the pushbutton is pressed, go to this function %% 
            
            %% STEP THREE
            myVar = 5;
            %% STEP FOUR
            assignin('caller','myVarX',myVar)
            %% STEP FIVE
            delete(app)
            
        end %% POINTER ONE

However, MATLAB give the following error;

Unrecognized function or variable 'myVar'.
Error in newt (line 5)
NewVar=myVar;

Upon debugging, I notice myVar has been succesfully transfer to the caller environment just before STEP FIVE. But, at the exit of the ButtonPushed function (POINTER ONE), the myVar at caller environment was cleared.

Appreciate if someone can shed some light to address this problem.

Answer 1

[Walter Roberson]

The "caller" of callbacks is the top level MATLAB session, not the function that created the app.

You will need to find a different approach.

[balandong]

Thanks for the quick reply.

Another approach I can think of is to first under the function ButtonPushed, to save the variable

save(SomePath\myVar.mat,'myVar');

Then under the function TestFunc, load the mat file.

load('myVar.mat')

However, I dont find this approach save and load to be effiecient and elegent.

Appreciate if you can suggest another approach that more effiecient and elegent.

Appreciate it.

[balandong]

Fyi, I also followed https://www.mathworks.com/matlabcentral/answers/441430-how-to-return-values-from-mlapp-to-the-m-caller#comment_767311. However, it seems not working MATLAB 2019b version,

[balandong]

Other approach, though not elegent as in

https://www.mathworks.com/matlabcentral/answers/441430-how-to-return-values-from-mlapp-to-the-m-caller#answer_358197