Function is not ready

[mark goldin]

I have the following pseudo code:

public function someTypeChange(event:IndexChangeEvent=null):void
{
someArrayCollection.filterFunction = someFilterFunction;
someArrayCollection.refresh();
}
public function someFilterFunction(item:Object):Boolean
{
                         .....
}
I have a component that consists of two elements: TextInput and Combo.
The code above is behind this component. someTypeChange is a listener for
combo change.
When I select a new value in the combo the above code works fine. But if I
call someTypeChange like this from combo:
override public function set data(value:*):void
{
super.value = value;
someTypeChange.call();
}
then I am getting:
Cannot access a property or method of a null object reference. and the
error line is:
someArrayCollection.filterFunction = someFilterFunction;

Any idea?

Thanks