What event tells me when any data changes in a mx:datagrid?

Question

I have a mx:datagrid that I need to have an event tell me when anything at all changes in the datagrid. The datagrid can be empty and as such may not have a dataprovider (=null) some of the time. I have looked at a variety of events but none seem to do what i want - can anyone suggest what event i should be listening for please?
many thanks,
Mark.

Answer 1

We have not formalized the concept of nested collections in Flex.  However,
let me amend my recommendation a bit.
Typically in a nested collection, the objects in the top-level collection
are not just collections but an object with some other reference data and
then a collection like:
    public class FamilyTreeItem
        public var name:String;
        public var children:ArrayCollection;
The top-level collection is listening for propertyChange events.  Typically,
as a data item gets modified, a propertyChange event is dispatched.  If the
data items do not dispatch propertyChange events, then the itemUpdated()
method is used.  Either way, the result is a COLLECTION_CHANGE event from
the top-level collection.
When you have a nested ArrayCollection, while that sub-ArrayCollection is
dispatching COLLECTION_CHANGE, nobody is listening for it at the top-level.
You can dispatch it yourself, or you can call itemUpdated() on the top-level
or dispatch a propertyChange.
The latter will be the most work, but most general.  Code in FamilyTreeItem
would attach a listener to the collection for COLLECTION_CHANGE and then
dispatch a propertyChange as appropriate.