How can I pass variables (declare in a pop up menu) in a pushbotton section of GUI ?

Hi, I am doing GUI which has a popup menu that allow the user to choose from several options (different type of steel), lets say I have three options each one has different values (Drho0, Ntot and Scalamobi). My coding is like this (for example):

function popupmenu1_Callback(hObject, eventdata, handles)
% hObject    handle to popupmenu1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hints: contents = cellstr(get(hObject,'String')) returns popupmenu1 contents as cell array
%        contents{get(hObject,'Value')} returns selected item from popupmenu1

 switch get(handles.popupmenu1,'Value') 

    case 304

 p1 =  -3.929e+12;
 p2 =   9.107e+12;
 p3 =    -7.5e+12;
 p4 =   2.771e+12;
 p5 =  -2.709e+11;
 S.Drho0=(p1*riduzione^4+p2*riduzione^3+p3*riduzione^2+p4*riduzione+p5);
 S.Ntot=1.311e-69*Drho0^(6.975);
 S.Scalamobi=1e-04; %%coefficiente di riscalamento che tiene conto della presenza di leganti

    case 316

 S.Drho0 = (2.8e11*(e)+1.57e10);
 S.Ntot  = (-5.23e8*(e)^2+ 1.76e9*(e) - 1.318e8);
 S.Scalamobi=1.2e-05;

   otherwise
 end

 set(handles.popupmenu, 'UserData', S);

I tried to use an old answer from matlabcentral: https://it.mathworks.com/matlabcentral/answers/38419-get-value-from-popup-menu-and-use-it-in-different-function. But I am getting an error when I try to access my variable in the push- button callback :

 S = get(handles.popupmenu1, 'UserData');     
 Drho0=S.Drho0;
 Ntot=S.Ntot;  
 Scalamobi=S.Scalamobi;

I am getting this error: "Struct contents reference from a non-struct array object". What am I doing wrong ? Thanks in advance

[Adam]

Which line throws the error? You can use

dbstop if error

to force the code to stop on the error line (or use the Breakpoints menu).

[Giuseppe Napoli]

Error in switchprova>pushbutton1_Callback (line 281) Drho0=S.Drho0;

I think that Matlab does not recognize the S. variable

Answer 1

[Adam]

I didn't notice this before. Maybe it is a typo in your question, but I will assume you just pasted in from your code:

set(handles.popupmenu, 'UserData', S);

...

S = get(handles.popupmenu1, 'UserData');

You are missing the '1' off the end of handles.popupmenu. I'm surprised this line does not cause an error though as I wouldn't have though it was valid syntax if you don't also have a graphics object called handles.popupmenu.

[Giuseppe Napoli]

I pasted from my code and I forgot to put the 1 at the end of popupmenu. But I am getting the same error, in the same line :

 S = get(handles.popupmenu1, 'UserData');     
 Drho0=S.Drho0;  % LINE 284
 Ntot=S.Ntot;

Struct contents reference from a non-struct array object.

Error in switchprova>pushbutton1_Callback (line 284) Drho0=S.Drho0;

[Adam]

I would recommend just using standard handle usage rather than attaching to the 'UserData' of a UI component - i.e.

handles.S = S;
guidata( hObject, handles );

in your popup callback, then

S = handles.S;

in your pushbutton callback, or just use it directly as handles.S if you prefer. I would name it something more meaningful personally too, but since you called it S I did the same.