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https://issues.apache.org/jira/browse/FLEX-34143?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13934436#comment-13934436
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Gary Yang commented on FLEX-34143:
----------------------------------

According to my knowledge, Flex Binding depend on two kinds of events:

1) PropertyChangedEvent, which will trigger binding when a)there is a 
[Bindable] for a class, and any of it's public property changed; b) a public 
property with [Bindable];

2) Any event with event type in property getter's [Bindable( 
event="eventTypeTriggeringBinding")], which will trigger binding when it is 
dispatched.

a binding is always:

        <fx:Binding source="a.b.c.d" destination~~~~

What I am expecting to know is which of [ a, b, c, d ] 's change triggering the 
handler, NOT the source event( could be anything event MouseDown, totally out 
of Binding's scope);

I'm sorry for the confusion.



> Give <fx:Binding /> an event handle.
> ------------------------------------
>
>                 Key: FLEX-34143
>                 URL: https://issues.apache.org/jira/browse/FLEX-34143
>             Project: Apache Flex
>          Issue Type: Improvement
>          Components: Data Binding
>            Reporter: Gary Yang
>   Original Estimate: 672h
>  Remaining Estimate: 672h
>
> 1st of all, Flex Binding is great!!!
> I am using it this way:
> >>>>>>>>>>>>>>>>>code>>>>>>>>>>>>
>  <fx:Script><![CDATA[
>         [Bindable("dataChange")]
>         public function get rowData():VLogicTreeGridRow{
>             return data as VLogicTreeGridRow;
>         }
>         private var _cellData:VLogicTreeGridCell;
>         [Bindable(event="cellDataChanged")]
>         public function get cellData():VLogicTreeGridCell{
>             return _cellData;
>         }
>         private function set rfrCellData( v:* ):void{
>             if( rowData != null
>                     && logicTreeGrid.columns != null && 
> logicTreeGrid.columns.length > 0
>                     && rowData.cellList != null && rowData.cellList.length > 0
>                     ){
>                 var idx:int = logicTreeGrid.columns.getItemIndex( 
> treeGridColLogic );
>                 var rt:VLogicTreeGridCell = rowData.cellList.getItemAt( idx ) 
> as VLogicTreeGridCell;
>                 if( _cellData != rt ){
>                     _cellData = rt;
>                     dispatchEvent( new Event( "cellDataChanged" ) );
>                 }
>             }
>         }
>         ]]></fx:Script>
>     <ui:layout>
>         <s:HorizontalLayout paddingTop="2" paddingBottom="2" paddingLeft="2" 
> paddingRight="2"/>
>     </ui:layout>
>     <fx:Binding source="logicTreeGrid.columns.length" 
> destination="rfrCellData"/>
>     <fx:Binding source="rowData.cellList.length" destination="rfrCellData"/>
> <<<<<<<<<<<<<<<code<<<<<<<<<<<<
> Because the destination of Binding tag can only be setters, I have to use it 
> this way if I want to handle changes from the Binding sources,  do you think 
> it's possible to add a handle for Binding tag so that I can see exactly what 
> event caused the change please?
> So that it can be like this
> >>>>>>>>>>>>>>>>>code>>>>>>>>>>>>
>         private function refreshCellData( ev:Event ):void{
>             if( ev is CollectionEvent ){
>                 
>             }
>             else if( ev is PropertyChangeEvent ){
>                 
>             }
>             if( rowData != null
>                     && logicTreeGrid.columns != null && 
> logicTreeGrid.columns.length > 0
>                     && rowData.cellList != null && rowData.cellList.length > 0
>                     ){
>                 var idx:int = logicTreeGrid.columns.getItemIndex( 
> treeGridColLogic );
>                 var rt:VLogicTreeGridCell = rowData.cellList.getItemAt( idx ) 
> as VLogicTreeGridCell;
>                 if( _cellData != rt ){
>                     _cellData = rt;
>                     dispatchEvent( new Event( "cellDataChanged" ) );
>                 }
>             }
>         }
>         ]]></fx:Script>
>     <ui:layout>
>         <s:HorizontalLayout paddingTop="2" paddingBottom="2" paddingLeft="2" 
> paddingRight="2"/>
>     </ui:layout>
>     <fx:Binding source="logicTreeGrid.columns.length" 
> changeHandle="refreshCellData"/>
>     <fx:Binding source="rowData.cellList.length" 
> changeHandle="refreshCellData"/>
> <<<<<<<<<<<<<<<code<<<<<<<<<<<<
> This is going to be very useful!!!



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