programmatic GUI callback function

I want to access the GUI control from the call back function. how can I do this. I got the below code from Matlab help but it gives an error when executed. How can I access the slider from the call back function.

function mygui()
   figure
   uicontrol('Style','slider','Callback',@display_slider_value);
end
function display_slider_value(hObject,callbackdata)
   newval = num2str(hObject.Value);
   disp(['Slider moved to ' newval]);
end

Answer 1

[Geoff Hayes]

Akshata - what is the error message? Note that if you are trying to get the current value of the slider, you could try using

 newval = num2str(get(hObject,'Value'));

The above assumes that the error has something to do with the current line that gets the newval.

[Chandrasekhar]

Hi, thanks for your reply. Even this gives an error. Error if found when I change the slider position on the GUI. Please find the error message below

Attempt to reference field of non-structure array.

Error in mygui>display_slider_value (line 6)
   newval = num2str(get(hObject.Value));

Error while evaluating uicontrol Callback

[Geoff Hayes]

The error message is indicating that you are trying to access a field of an object that is not a structure. In your case, hObject is not a structure and so you can't access Value from it. Which version of MATLAB are you using?

To get around this error, replace your line with

 newval = num2str(get(hObject,'Value'));

as described above.

[Chandrasekhar]

Thanks for the reply. It worked I am using 2012b

Answer 2

[Sean de Wolski]

I fyou're using a version of MATLAB < R2014b, hObject.Value won't work. That syntax is added in R2014b.

If your company/university if current on maintenance, you should be able to upgrade at no additional cost. If not, use get(hObject,'Value')

[Chandrasekhar]

thanks, it worked