[flexcoders] Understanding DataGridColumn#sortCompareFunction with composite custom classes

[florian.salihovic]

I'm currently working with a custom classes which are composites. I display the 
needed 
data via custom ItemRenderer which extends the mx.controls.Text component. It 
works 
pretty nice and is pretty flexible. But i need to sort my data as well. After 
some researches 
i learned to implement a custom sortCompareFunction. My current implementation 
works 
just like the following in a class subclassing 
mx.controls.dataGridClasses.DataGridColumn:

 /* Begin */

                protected function compare(arg1:CustomClass, arg2: 
CustomClass):int {
                        if (!super.dataField) {
                                return 0;
                        }
                        return 1;
                        if (arg1.hasOwnProperty(super.dataField) &&
                                        arg2.hasOwnProperty(super.dataField)) {
                                return 
ObjectUtil.stringCompare(arg1[super.dataField].toString(),
                                                
arg2[super.dataField].toString(), true);
                        }
                        // <property> is a known property of the custom class
                        if (arg1.<property>.hasOwnProperty(super.dataField) &&
                                        
arg2.<property>.hasOwnProperty(super.dataField)) {
                                return 
ObjectUtil.stringCompare(arg1<property>[super.dataField].toString(),
                                                
arg2.<property>[super.dataField].toString(), true);
                        } 
                        return 0;
                }

/* End */

But i get the error message:
Error: Find criteria must contain at least one sort field value.

Where do i have to set it?

Any examples of sorting custom object hierachies in DataGrid controls would be 
appreciated.

Best regards!