uicontol callback errors in different Matlab versions

I have a short GUI with input fields, radio buttons and push buttons:

function []=my_gui()
S.fh = figure('units','pixels',...
                    'position',[100 300 600 500],...
                    'menubar','none',...
                    'name','my_gui',...
                    'numbertitle','off',...
                    'resize','off',...
                    'deletefcn','');
S.field = uicontrol('style','edit',...
                    'unit','pix',...
                    'position',[10 450 50 30],...
                    'string','');
S.radio = uicontrol('style','radiobutton',...
                    'unit','pix',...
                    'position',[25 410 120 30],...
                    'string','');
S.button = uicontrol('style','push',...
                    'unit','pix',...
                    'position',[10 10 80 30],...
                    'string','Run');
set(S.button,'callback',{@run_function,S});

function [] = run_function(varargin)
assignin('base','data_in',varargin);
S = varargin{3};  % Get the structure.
my_field = str2double(get(S.field,'string'));
my_radio=S.radio.Value;
assignin('base','data_out',[my_field,my_radio]);

The GUI executes with no problems in R2015a, but when it is executed in R2012a the following message appears:

Attempt to reference field of non-structure array.
Error in my_gui>run_function (line 28)
my_radio=S.radio.Value;
Error while evaluating uicontrol Callback

Looking at the 'data_in' and 'data_out' arrays in each version shows that in 2012a the uicontrol property in data_in{1} is no longer there. Can anyone advise on the issue, or if I require a workaround?

Answer 1

[Geoff Hayes]

Richard - there were changes to how GUI elements are managed around R2014b (I think as I'm still on R2014a - see http://www.mathworks.com/help/matlab/graphics_transition/graphics-handles-are-now-objects-not-doubles.html for details) so what you can code with the later versions is not valid for earlier ones. For older versions, if you have the handle to the control, you would need to use the get function to fetch a specific property. For example, if hText1 is a handle to a text control, then you would do

 myText = get(hText1,'String');

to get the string contents within this control which is like what you are doing at

 my_field = str2double(get(S.field,'string'));

For the radio button, you would do

 my_radio = get(S.radio, 'Value');