Flex动态创建类对象

Flex动态创建类对象
2010年08月07日
　　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：      package test { public dynamic class DynamicObject { public function DynamicObject() { trace("DynamicObject is created!"); } } } 输出结果：  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_applicationCompl ete()[C:\Documents and Settings\Administrator\My Documents\Workspace\eclipse\ccgc\src\TestMain.mxml :2] at flash.events::EventDispatcher/dispatchEventFunctio n() at flash.events::EventDispatcher/dispatchEvent() at mx.core::UIComponent/dispatchEvent() at mx.managers::SystemManager/preloader_preloaderDone Handler()[C:\autobuild\3.5.0\frameworks\projects\fr amework\src\mx\managers\SystemManager.as:3140] at flash.events::EventDispatcher/dispatchEventFunctio n() at flash.events::EventDispatcher/dispatchEvent() at mx.preloaders::Preloader/displayClassCompleteHandl er()[C:\autobuild\3.5.0\frameworks\projects\framewo rk\src\mx\preloaders\Preloader.as:435] at flash.events::EventDispatcher/dispatchEventFunctio n() at flash.events::EventDispatcher/dispatchEvent() at mx.preloaders::DownloadProgressBar/timerHandler()[ C:\autobuild\3.5.0\frameworks\projects\framework\sr c\mx\preloaders\DownloadProgressBar.as:1451] at mx.preloaders::DownloadProgressBar/initCompleteHan dler()[C:\autobuild\3.5.0\frameworks\projects\frame work\src\mx\preloaders\DownloadProgressBar.as:1503] at flash.events::EventDispatcher/dispatchEventFunctio n() at flash.events::EventDispatcher/dispatchEvent() at mx.preloaders::Preloader/dispatchAppEndEvent()[C:\ autobuild\3.5.0\frameworks\projects\framework\src\m x\preloaders\Preloader.as:291] at mx.preloaders::Preloader/appCreationCompleteHandle r()[C:\autobuild\3.5.0\frameworks\projects\framewor k\src\mx\preloaders\Preloader.as:443] at flash.events::EventDispatcher/dispatchEventFunctio n() 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：
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