Oh, I just stepped through Observe, and I guess the standard binding
mechanism calls the source setter again, which calls the handler.
On Thu, Aug 14, 2008 at 6:49 AM, Richard Rodseth <[EMAIL PROTECTED]> wrote:
> Thanks guys.
>
> Can someone explain how ac:Observe (which this is based on) works? i.e.
> what triggers the handler call when somethng in the middle of the source
> binding expression changes (eg. "b" in "{a.b.c.myCollection}"? I don't see
> any event handlers, and there's a mysterious execute() method in the parent
> class (Observer).
>
> And would your version below also fire when b changes?
>
> Otherwise, Josh's example works too, but the collection event is the only
> trigger.
>
>
> On Thu, Aug 14, 2008 at 12:12 AM, Dennis van Nooij <[EMAIL PROTECTED]>wrote:
>
>> try this:
>>
>> package com.adobe.ac
>> {
>> import mx.events.CollectionEvent;
>> import mx.collections.ArrayCollection;
>> import flash.events.Event;
>> import mx.core.Application;
>> import mx.core.UIComponent;
>>
>>
>> /**
>> *
>> * monitors Collections and react on reassining of the variable
>> * and changes in the collection which are bindable
>> *
>> */
>> public class ObserveCollection extends Observer
>> {
>> private var _handler : Function;
>> private var _source : Object;
>>
>> override public function get handler() : Function
>> {
>> return _handler;
>> }
>>
>> public function set handler( value : Function ) : void
>> {
>> _handler = value;
>> if( value != null )
>> {
>> isHandlerInitialized = true;
>> if( isHandlerInitialized && isSourceInitialized )
>> {
>> callHandler();
>> }
>> }
>> }
>>
>> override public function get source() : Object
>> {
>> return _source;
>> }
>>
>> public function set source( value : Object ) : void
>> {
>> if (_source != null){
>>
>>
>> _source.removeEventListener(CollectionEvent.COLLECTION_CHANGE,collectionChangeHandler);
>>
>> }
>> _source = value;
>>
>>
>> _source.addEventListener(CollectionEvent.COLLECTION_CHANGE,collectionChangeHandler);
>>
>> isSourceInitialized = true;
>>
>> if( isHandlerInitialized && isSourceInitialized )
>> {
>> callHandler();
>> }
>> }
>>
>> protected override function callHandler() : void
>> {
>> try
>> {
>> handler.call( null, source );
>> }
>> catch( e : Error )
>> {
>> delay( e );
>> }
>> }
>>
>> protected override function delay( e : Error ) : void
>> {
>> UIComponent( Application.application ).callLater( throwException, [
>> e ] );
>> }
>>
>> private function throwException( e : Error ) : void
>> {
>> throw e;
>> }
>>
>> private function collectionChangeHandler (event:Event) : void
>> {
>>
>> callHandler();
>> }
>>
>>
>> }
>> }
>>
>> cheers,
>> Dennis
>>
>>
>> --- In [email protected] <flexcoders%40yahoogroups.com>, "Alex
>> Harui" <[EMAIL PROTECTED]> wrote:
>> >
>> > Never used Observe, but if it implements IMXMLObject or you subclass and
>> > do so, then you can use it in MXML
>> >
>> >
>> >
>> > ________________________________
>> >
>> > From: [email protected] <flexcoders%40yahoogroups.com>[mailto:
>> [email protected] <flexcoders%40yahoogroups.com>] On
>> > Behalf Of Richard Rodseth
>> > Sent: Wednesday, August 13, 2008 4:16 PM
>> > To: [email protected] <flexcoders%40yahoogroups.com>
>> > Subject: [flexcoders] Observing collections
>> >
>> >
>> >
>> > For some reason I have an aversion to adding event listeners in
>> > ActionScript, favouring binding expressions and the Observe tag from
>> > Adobe Consulting. Not sure how rational this is, but there you have it.
>> > Binding is just so damn elegant.
>> >
>> > However, collections are a problem. It seems that so often you want to
>> > update something if either the collection itself or its contents
>> > changes, and you don't really care about the details of the change.
>> >
>> > I suppose if you're a DataGrid watching its dataprovider you do care and
>> > can minimize updates, but in many of the use cases I've encountered,
>> > that's not the case - my observer is going to do something with the
>> > whole collection (or maybe I've just been lazy about exploiting possible
>> > optimizations).
>> >
>> > Is there anything like the Observe tag that can be instantiated in MXML
>> > and can trigger a function call on a COLLECTION_CHANGE event?
>> >
>>
>>
>>
>
>
