Flex single-instance mode

Single instance mode in Flex, common model layer instances: Single instance mode in Flex, common model layer instances:
Package models
{
Import flash. events. EventDispatcher;

Import mx. collections. ArrayCollection;

Import vo. articlesVO;
Import vo. linksVO;
[Bindable]
Public class ModelLocator extends EventDispatcher
{
Public static var _ instance: ModelLocator;
Public static function getInstance (): ModelLocator {
If (_ instance = null ){
_ Instance = new ModelLocator ();
}
Return _ instance;
}
Public var total: int;
Public var isLogin: Boolean = false;
Public var articles: ArrayCollection;
Public var selectedArticle: articlesVO;
Public var categories: ArrayCollection;
Public var links: ArrayCollection;
Public var selectedLink: linksVO;
}
}
Class ..

<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;import&nbsp;models.ModelLocator; <br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;internal&nbsp;function&nbsp;initApp():void{ <br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;var&nbsp;instance:ModelLocator&nbsp;=&nbsp;ModelLocator.getInstance(); <br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;trace(instance.isLogin);//获得isLogin <br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;} <br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;