Sorting a DataGrid without changing the content

Question

I have a datagrid which is shown in a chart. I'd like to have it sorted upside down the dataField "x" without changing the chart, which is bound to the same arrayCollection. How can I do this without changing the chart?
<mx:DataGrid sortableColumns="false"  width="480" height="156" dataProvider="{myArrayCollection}" editable="false" y="581" enabled="true" x="10">
          <mx:columns>
                <mx:DataGridColumn id="col1" dataField="x" headerText="Trade #" />
                <mx:DataGridColumn id="col2" dataField="p" headerText="Price" />
                <mx:DataGridColumn id="col3" dataField="n" headerText="Users" />
            </mx:columns>
</mx:DataGrid>
thanks
nicolas

Answer 1

ArrayCollection is a view of a source Array.  If you create a second view, it can have a different sort order because sort and filters are properties of a view.
Just assigning AC2 = AC1 simply has AC2 referencing the same view so sorting will have an effect on all consumers of that view.  However, if you do:
AC2 = new ArrayCollection();
AC2.list = AC1.list
then you can sort AC2 and AC1 will not reflect the sort and vice-versa.  But, if you add an item to AC2 or AC1 it will be reflected in the other AC.  If you modify a property of an item in one AC, the other AC will see it.
If you do:
AC2 = new ArrayCollection()
AC2.source = AC1.source
You can also sort AC2 and AC1 will not reflect the sort and vice-versa.  But, if you add an item to AC2 or AC1, the other will not reflect that change unless you force an update on the other.  Same is true if you modify a property on an item in the AC.  The other AC won't know about it until you force an update.
If you want to modify properties of an item in one AC and not every have it reflected in the other AC, then you should do a copy as the previous responder suggested.  I believe you want to use the pattern that assings AC2.list = AC1.list.
Alex Harui
Flex SDK Developer
Adobe Systems Inc.
Blog: http://blogs.adobe.com/aharui