Khanh - the problem is that edit is an array of strings to edit text control handles and is not an array of the handles themselves. So the error message makes sense. If you want to create an array of the handles then just do
editHandles = [handles.edit1, handles.edit2, handles.edit3, handles.edit4, handles.edit5, handles.edit6, handles.edit7, handles.edit8];
Alternatively, if you are interested in only those handles that are named edit*, then you could replace the above with
editHandles = findobj(handles.figure1, '-regexp', 'Tag', 'edit[0-9]');
where we find all the (child) objects of (parent) of the GUI (handles.figure1) whose Tag matches the expression edit with a numeric suffix. The order is possibly with the last added edit control first, so you may need to do some additional sorting or just be aware that the order of the edit text controls isn't handles.edit1, handles.edit2, etc.
