Attempt to reference field of non-structure array - the get command

I'm programming a GUI created in GUIDE with MatLab2014, and upon a button-click a series of GET commands store information from the GUI (checkbox statuses, for the sake of fixing this error):

eeps_check = (get(handles.eeps_check,'val')); 
tracefile_check = (get(handles.tracefile_check,'val'));
lambda_check = (get(handles.lambda_check,'val'));

now, I know the syntax of 'handles.eeps_check' must change somehow, as i get an error:

Attempt to reference field of non-structure array

MatLab is interpreting 'handles' as a struct, and 'eeps_check' as a field or something to that effect. This did not happen using MatLab2013.

So how should my syntax change such that i can store the information from checkboxes with handles 'eeps_check', 'Lambda_check', and 'tracefile_check' as variables in the workspace?? Thanks in advance.

[Geoff Hayes]

Jacob - the error message is saying something a little different: Attempt to reference field of non-structure array. The code is treating (presumably handles) as if it were a structure with fields, when in fact, handles is not a structure and has been (perhaps/probably) set to the empty matrix. For example,

 >> handles = [];
 >> handles.geoff
 Attempt to reference field of non-structure array.

If handles were a structure and the code attempted to obtain information on a field that doesn't exist within the structure, you would observe a different error message

 >> handles.x = 42;
 >> handles.y
 Reference to non-existent field 'y'.

If you are sure that this error originates in the above three lines of code, then place a breakpoint there and let the GUI run. When it pauses at the first line, check the handles variable. Is it a struct, or is it empty? If the latter, there may be a problem with how the GUI is being initialized/run. Are you doing this from the Command Line, or through GUIDE? If the former, what are you typing in? Have you uncommented the uiwait function call in the OpeningFcn of your GUI which can delay the proper initialization of the GUI?

[Jacob Capra]

'handles' is not a variable, it is merely the syntax to call a handle. for instance:

>> get(handles.example,'string')

would get the value that the handle 'example' represents ( I am assuming it is a string in the line above).

[Geoff Hayes]

No, if you are using GUIDE to design your GUI, then handles is typically an input variable/parameter to the majority of callbacks. It is a structure that manages all of the GUI-defined handles to individual widgets (push buttons, edit fields, list boxes, etc.) and it can also be used by the user to manage user-defined fields (like images, results of calculations, etc. that need to be shared between callbacks).

For example, if I create a simple GUI with a push button and a edit field, then the callback for the push button is

 % --- Executes on button press in pushbutton1.
 function pushbutton1_Callback(hObject, eventdata, handles)
 % hObject    handle to pushbutton1 (see GCBO)
 % eventdata  reserved - to be defined in a future version of MATLAB
 % handles    structure with handles and user data (see GUIDATA)

Note the comment for the third input parameter. If I add some dummy code here and put a breakpoint at that line, I can then view what handles really is when the debugger pauses here

 K>> handles

 handles = 
        figure1: 185.00244140625
          edit1: 8.0037841796875
    pushbutton1: 186.00244140625
         output: 185.00244140625

 K>> class(handles)

 ans =
    struct