To go back to my city/country situation, let us say I have chosen the first main category ‘Italy’ and the third sub-category ‘Venice’.
If I now change the main category from Italy to Greece, this repopulates the sub-category with the cities of Greece, and the select item still shows the third sub-category item, now perhaps ‘Heraklion’, but there is no way to inform the view function to change the information,shown for this item, unless I have the index and can pass it to the view function.
Your initial suggestion was that changing the main category could result in a ‘No City Selected’ view, but if possible I want to do better than that and show the relevant item.