Flex动态创建类对象

自ActionScript 3开始，eval函数就被取消了，这样就不能像原来那样利用字符串动态的创建对象了，但利用函数flash.utils.getDefinitionByName仍可以根据类型名称动态地创建类对象实例，下面看一个例子：

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" minWidth="955" minHeight="600" applicationComplete="application1_applicationCompleteHandler(event)">
<mx:Script>
<!--[CDATA[
import flash.utils.getDefinitionByName;

import mx.events.FlexEvent;

import test.DynamicObject;
protected function application1_applicationCompleteHandler(event:FlexEvent):void
{

var typeRef:Class = getDefinitionByName("test.DynamicObject") as Class;
new typeRef();
// new DynamicObject();
}
]]-->
</mx:Script>
</mx:Application>

package test
{
public dynamic class DynamicObject
{
public function DynamicObject()
{
trace("DynamicObject is created!");
}
}
}

输出结果：

DynamicObject is created!
DynamicObject is created!

其实这样的输出结果，没什么意外的。接下来将“new DynamicObject();”注释掉继续执行，以下是输出解决：

ReferenceError: Error #1065: Variable DynamicObject is not defined.
at global/flash.utils::getDefinitionByName()
at TestMain/application1_applicationCompleteHandler()[C:/Documents and Settings/Administrator/My Documents/Workspace/eclipse/ccgc/src/TestMain.mxml:14]
at TestMain/___TestMain_Application1_applicationComplete()[C:/Documents and Settings/Administrator/My Documents/Workspace/eclipse/ccgc/src/TestMain.mxml:2]
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at mx.core::UIComponent/dispatchEvent()
at mx.managers::SystemManager/preloader_preloaderDoneHandler()[C:/autobuild/3.5.0/frameworks/projects/framework/src/mx/managers/SystemManager.as:3140]
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at mx.preloaders::Preloader/displayClassCompleteHandler()[C:/autobuild/3.5.0/frameworks/projects/framework/src/mx/preloaders/Preloader.as:435]
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at mx.preloaders::DownloadProgressBar/timerHandler()[C:/autobuild/3.5.0/frameworks/projects/framework/src/mx/preloaders/DownloadProgressBar.as:1451]
at mx.preloaders::DownloadProgressBar/initCompleteHandler()[C:/autobuild/3.5.0/frameworks/projects/framework/src/mx/preloaders/DownloadProgressBar.as:1503]
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at mx.preloaders::Preloader/dispatchAppEndEvent()[C:/autobuild/3.5.0/frameworks/projects/framework/src/mx/preloaders/Preloader.as:291]
at mx.preloaders::Preloader/appCreationCompleteHandler()[C:/autobuild/3.5.0/frameworks/projects/framework/src/mx/preloaders/Preloader.as:443]
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at mx.core::UIComponent/dispatchEvent()
at mx.core::UIComponent/set initialized()
at mx.managers::LayoutManager/doPhasedInstantiation()
at Function/http://adobe.com/AS3/2006/builtin::apply()
at mx.core::UIComponent/callLaterDispatcher2()
at mx.core::UIComponent/callLaterDispatcher()

之所以会出错，是因为在Flex编译程序时会自行删除一些未使用的，这时在动态创建对象时就会因缺失对象的类型而创建失败。之前的代码之所以执行成功，是因为类型DynamicObject在代码中显示地被使用，所以类型信息DynamicObject在编译时不会被删除。

其实还有一种方法来保证类型信息的存在，就是利用编译参数，也可以保证程序正常执行：

-includes=info.knightrcom.puppet.PushdownWinGamePinocchio