error: refernce to non existent field (handles) GUI

hey i am just a beginner so please help my silly question too. i have two radio buttons in my gui and i want to know which one is selected i found a code online but the variable in which i store the value remain local to that 'selectionChange' function

function image_type_SelectionChangeFcn(hObject, eventdata)
  handles= guidata(hObject);
 switch get(eventdata.NewValue, 'Tag' )
 case 'rgbbutton'
 handles.im='RGB'; 
 case 'grayscalebutton'
 handles.im='grayscale';     
 end
 disp(handles.im);
guidata(hObject,handles);

and hence when i call 'handles.im' in function 'Combine_callback' it gives the error below

reference to non-existent field 'im'

the combine_callback code is as follows

function combine_Callback(hObject, eventdata, handles)
handles=guidata(hObject);
im=handles.im;

disp(im);

please help. this is my project and i need to execute it!

[Geoff Hayes]

Preshma - are you sure that the image_type_SelectionChangeFcn is being called and that the handles.im is being set? I placed your above code in a simple GUI and it did work. When you created the two radio buttons, did you put them in a Button Group panel?

Answer 1

[Image Analyst]

Don't call guidata immediately. Try this:

function image_type_SelectionChangeFcn(hObject, eventdata)
    radio1 = get(handles.rgbbutton, 'Value');
    radio2 = get(handles.grayscalebutton, 'Value');

    if radio1
        handles.im='RGB'; 
    elseif radio2 
        handles.im='grayscale';  
    else
       % Should not get this case, but just for robustness...
       handles.im = 'Unknown';   
    end
    disp(handles.im);
    guidata(hObject,handles);