Specifying class properties in MXML elements instead of attributes (e.g. DataGridColumns)

Question

Hi there,
In all the examples I've seen so far, specifying the columns
for a
DataGrid is done as follows:
<mx:DataGrid>
<mx:columns>
<mx:DataGridColumn />
<mx:DataGridColumn />
<mx:columns>
</mx:DataGrid>
However, I'm wonder whether there's a way to express the data
grid
columns simply as an _attribute_ value on the
<mx:DataGrid> element?
If not, does anybody know of an explanation of the syntax for
setting
class properties when they are not set as attributes?
For example, since "columns" is a property of the DataGrid
class, but
it is set via an XML element, and not via an XML attribute, I
would
assume you can do something similar for other properties.
However, I
can't seem to find official documentation on this in the Flex
3
Language Reference.
Joubert

Answer 1

This works:
<mx:Array id="theMXMLColumns">
<mx:DataGridColumn headerText="Column 1" />
<mx:DataGridColumn headerText="Column 2" />
</mx:Array>
<mx:DataGrid id="dg2" columns="{theMXMLColumns}" />
However, the "columns" property of DataGrid must be an array,
and arrays are not bindable, so ActionScript updates to the array
would not be shown. e.g. This will not work:
<mx:Script>
<![CDATA[
import mx.collections.*;
import mx.controls.dataGridClasses.*;
private var theASColumns:Array;
private function doCreationComplete():void{
var dgc:DataGridColumn;
theASColumns = new Array();
dgc = new DataGridColumn();
dgc.headerText = "Column 1";
theASColumns.push(dgc);
dgc = new DataGridColumn();
dgc.headerText = "Column 2";
theASColumns.push(dgc);
]]>
</mx:Script>
<mx:DataGrid id="dg" columns="{theASColumns}" />