Trick with static class (singleton) binding: how to bind some singleton instance property to any application variable
Problem
Common problem with static classes - they "ignore" binding mechanism.
Solution
Create (or access via refference) instance as app public variable and bind it/to using <mx:Binding> (or <s:Binding> for SDK 4)
Detailed explanation
So, common problem is developer has some static class or singleton, for exaple named "NodeSystemModelLocator" with public public property (implemented via getter/setter) "selectedGene". This class implements model locator pattern for some application. Developer should bind mentioned property to some interface variable (some view controller property). In this case solution has several steps:
1) Add [Bindable] to model static class declaration:
[Bindable]
public class NodeSystemModelLocator extends EventDispatcher{
private static var modelLocator : NodeSystemModelLocator;
public static function getInstance() : NodeSystemModelLocator
{
if ( modelLocator == null )
{
modelLocator = new NodeSystemModelLocator();
}
return modelLocator;
}
private var _selectedGene : GeneVO;
public function get selectedGene():GeneVO{
return _selectedGene;
}
public function set selectedGene(gene:GeneVO):void{
_selectedGene = gene;
//some code
}
}
2) in main app add variable to store singleton instance:
<mx:Script>
<![CDATA[
//some code
[Bindable]
public var _model : NodeSystemModelLocator;
]]>
</mx:Script>
3) in main app add mxml binding:
<mx:Binding destination="navView.deleteGeneCB.selectedItem" source="_model.selectedGene"/>
navView instance declared in main app layout as
<view:NodeSystemNavigationView top="0" right="0" id="navView"/>
and deleteGeneCB is a combo box instance id there.
So, now we have 2-way binding for model (singleton) instance variable and visual component property. And it works properly.
