correct: 1,2,3,4,11,12,21
incorrect: 1,11,12,2,21,3,4

private function sortCompareFunction(obj1:Object, obj2:Object, column:GridColumn): int {
	var p1:Number = obj1[column.dataField];
	var p2:Number = obj2[column.dataField];

	if (p1 < p2){
		return -1;
	} else if (p1 > p2){
		return 1;
	} else {
		return 0;
	}
}

<s:DataGrid>
	<s:columns>
		<s:ArrayList>
			<s:GridColumn dataField="d1" headerText="h1" sortCompareFunction="sortCompareFunction"/>
			<s:GridColumn dataField="d2" headerText="h2" sortCompareFunction="sortCompareFunction"/>
			<s:GridColumn dataField="d3" headerText="h3" sortCompareFunction="sortCompareFunction"/>
		</s:ArrayList>
	</s:columns>
</s:DataGrid>