Ok - I think I'm making some headway now. Here's hoping this helps someone else with similar problems.
For ages I've been plagued by 'odd' databinding problems. Things would work most of the time - then fail for 'no reason'... Playing around tonight, I noticed some behaviors that I think explain a bunch of the problems I've been having. Perhaps others have had the same problems, so here it is in a nutshell: It appears eventlisteners and databinding bind to the object - and _not_ the identifier/label. This holds true even for accessor based properties. This means that having a 'currentRec', that gets reset to point to each object in a list for instance, can be very dangerous. for instance, if you have var currRec:MyRecord and you use it in mxml databindings, the bindings get applied to the object currRec reference when the component was initialized! If you later move another record into currRec, your databindings still point to the FIRST object. Could someone from Adobe confirm this? Below is a little toy I wrote to test this stuff. The trace output supports the statement above. Notice how after the assignment: baz = bar, we start getting trace output from the 'bar' eventlisteners. The 'baz' eventlisteners no longer fire. Play around with some of the commented out statements, and see how the output changes - I was really surprised that statement ordering in the setter made a difference! Btw, If anyone can tell me why the PropertyChange handler doesn't fire, I'd appreciate it! I thought 'PropertyChange' was the default event used by databinding? Trace output: Assign 1 model to another BAZ:Model Changed Event Generated! Event type: ModelChanged Assign to accessorType BAR:Model Changed Event Generated! Event type: ModelChanged Assign to var based property - Why doesn't the 'PropertyChange' handler fire? call ModelBase.set() BAR:Model Changed Event Generated! Event type: ModelChanged Test completed baz.accessorType: Steve BAR:Model Changed Event Generated! Event type: ModelChanged ================================================== ModelBase1.mxml <?xml version="1.0" encoding="utf-8"?> <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"; layout="absolute" creationComplete="setup()"> <mx:Script> <![CDATA[ import ModelBase; import DerivedClass; import mx.binding.utils.BindingUtils; import flash.events.*; private var _baz:DerivedClass = new DerivedClass(); [Bindable (event="ModelChanged")] public function get baz():DerivedClass { return _baz; } public function set baz(v:DerivedClass):void { // Notice you get different handlers depending on which dispatch you use // also, the 'this.baz' is needed because 'this.dispatch' or 'dispatch' would // dispatch on the root tag (this = mx:Application) this.baz.dispatchEvent( new Event("ModelChanged")); _baz = v; //this.baz.dispatchEvent( new Event("ModelChanged")); } [Bindable (event="ModelChanged")] private var foo:DerivedClass = new DerivedClass(); [Bindable (event="ModelChanged")] private var bar:DerivedClass = new DerivedClass(); public function setup():void { foo.addEventListener('ModelChanged', foomodelChanged); foo.addEventListener('PropertyChange', foopropertyChanged); bar.addEventListener('ModelChanged', barmodelChanged); bar.addEventListener('PropertyChange', barpropertyChanged); baz.addEventListener('ModelChanged', modelChanged); baz.addEventListener('PropertyChange', propertyChanged); trace("Assign 1 model to another"); baz = bar; trace("\nAssign to accessorType"); baz.accessorType = "Steve"; trace("\nAssign to var based property - Why doesn't the 'PropertyChange' handler fire?"); baz.varType = 'Whee!'; trace("call ModelBase.set()"); baz.set(foo); trace("\nTest completed baz.accessorType: " + baz.accessorType); } public function changeit():void { //bar.accessorType = 'Changed'; baz.accessorType = 'Changed'; } public function propertyChanged(e:Event):void { trace("BAZ:Binding detected a change!"); } public function modelChanged(e:Event):void { trace("BAZ:Model Changed Event Generated! Event type: " + e.type); } public function barpropertyChanged(e:Event):void { trace("BAR:Model Changed Event Generated! Event type: " + e.type); } public function barmodelChanged(e:Event):void { trace("BAR:Model Changed Event Generated! Event type: " + e.type ); } public function foopropertyChanged(e:Event):void { trace("FOO:Model Changed Event Generated! Event type: " + e.type ); } public function foomodelChanged(e:Event):void { trace("FOO:Model Changed Event Generated! Event type: " + e.type ); } ]]> </mx:Script> <!-- I'd have expected this to work, but it doesn't as the object referenced by baz changes --> <!--mx:Button id='b1' label="{baz.accessorType}" x="53" y="109"/> <mx:Button id='b2' label="{baz.varType}" click="changeit()" x="53" y="130" / --> <!-- This works since bar always refers to the same object --> <mx:Button id='b1' label="{bar.accessorType}" x="53" y="109"/> <mx:Button id='b2' label="{bar.varType}" click="changeit()" x="53" y="130" /> </mx:Application> ================================================== DerivedClass.as: package { import flash.events.Event; public class DerivedClass extends ModelBase { private var _aType:String = "Start"; // How do we bind to a custom event in mxml ? //[Bindable (event="ModelChanged")] - doesn't work for ModelBase1.mxml [Bindable] public var varType:String = "variable Based"; [Bindable (event="ModelChanged")] public function set accessorType(v:String):void { _aType = v; dispatchEvent( new Event("ModelChanged")); } public function get accessorType():String { return _aType; } public function DerivedClass() { // } } } ================================================== ModelBase.as package { import flash.utils.*; import flash.events.*; public class ModelBase extends EventDispatcher { public var dummy1:String = 'String'; public function ModelBase() { } public function set(o:ModelBase):void { this.dummy1 = o.dummy1 + " blah"; dispatchEvent( new Event('ModelChanged')); } } }
