How to get the previous value entered from the callback function?

Question

I know this is probably a simple problem, but I'm new to Matlab's GUI and basically want to get the old value that was previously stored in the text box to replace the entered value. For instance.

• The text field contains a valid string,
• The user enters an invalid string,
• The callback function, checking the input and implementing a new input is an error and returns to the previous value.

How should this be implemented or done? Atm I just use the values ​​get and set property. The following is sample code:

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

% Hints: get(hObject,'String') returns contents of sampledist as text
%        str2double(get(hObject,'String')) returns contents of sampledist as a double

input = str2double(get(hObject,'String'));
if(input < 0 || input > 500)
    errordlg('Sampled Dist. must be > 0 and < 500','Sample Dist - Input Error');
    set(handles.sampledist,'String',['10']); %<--- I would like this value 10 to be the previous entry!
    guidata(hObject,handles);
else
   set(handles.sampledist,'String',['',input]);
   guidata(hObject,handles);
end

Answer 1

sampledistPrev .

openingFcn GUI , :

handles.sampledistPrev = 10; %# or whatever you choose as default value
%# if you want, you can set the default value to the GUI, so that you only need 
%# to change it at one point, if necessary, like so:
set(handles.sampledist,'String',num2str(handles.sampledistPrev));
%# don't forget to save the handles structure at the end of the openingFcn
guidata(hObject,handles)

:

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

% Hints: get(hObject,'String') returns contents of sampledist as text
%        str2double(get(hObject,'String')) returns contents of sampledist as a double

input = str2double(get(hObject,'String'));
if(input < 0 || input > 500)
    errordlg('Sampled Dist. must be > 0 and < 500','Sample Dist - Input Error');
    set(handles.sampledist,'String',num2str(handles.sampledistPrev)); %reset value be the previous entry!
    guidata(hObject,handles); %# Note that you don't need to save the handles structure unless
                              %# you have changed a user-defined value like sampledistPrev
                              %# It may still be useful to do it so you always remember
else
   set(handles.sampledist,'String',['',input]);
   %# also update the reset value
   handles.sampledistPrev = input;
   guidata(hObject,handles);
end

Answer 2

" " "UserData" , :

---

function sampledist_Callback(hObject, eventdata, handles)
    input = str2double(get(hObject,'String'));
    if (input < 0 || input > 500)
        errordlg('Sampled Dist. must be > 0 and < 500','Sample Dist - Input Error');
        val=get(hObject,'UserData');
        if isempty(val)
            val='';
        end
        set(hObject,'String',val); %<--- This is where you'd like to set the previous entry value!
        guidata(hObject,handles);
    else
        input=num2str(input);
        set(handles.sampledist,'String',input,'UserData',input);
        guidata(hObject,handles);
    end
end

---

% Y.T.