describeType函数在adobe官方在线文档上的定义如下：生成描述ActionScript对象(命令为方法的参数)的XML对象，此方法实现ActionScript语言的反射编程概念。
这个方法的应用场景可能是这样的：
定义一个方法，解析很多邮件的消息，很多消息的内容格式又是一致的(需要实现方法的共用)，那么定义下面一系列的方法了。
public function parseEmail_1():void {}
public function parseEmail_2_3_4_5():void {}
public function parseEmail_10_11_12():void {}
…
如何根据邮件格式的消息，直接就调用了相应的函数？那首先需要有一个对象存储了该类的所有方法，然后查找到包含此id的方法，之后调用它即可。
示例：
建立一个名为“describeType_Test”的ActionScript工程。使用describeType(类名)即可获得到该类的所有相关信息
<type name="describeType_Test" base="Class" isDynamic="true" isFinal="true" isStatic="true">
<extendsClass type="Class"/>
<extendsClass type="Object"/>
<accessor name="prototype" access="readonly" type="*" declaredBy="Class"/>
<factory type="describeType_Test">
<extendsClass type="flash.display::Sprite"/>
<extendsClass type="flash.display::DisplayObjectContainer"/>
<extendsClass type="flash.display::InteractiveObject"/>
<extendsClass type="flash.display::DisplayObject"/>
<extendsClass type="flash.events::EventDispatcher"/>
<extendsClass type="Object"/>
<implementsInterface type="flash.events::IEventDispatcher"/>
<implementsInterface type="flash.display::IBitmapDrawable"/>
<accessor name="useHandCursor" access="readwrite" type="Boolean" declaredBy="flash.display::Sprite"/>
<accessor name="root" access="readonly" type="flash.display::DisplayObject" declaredBy="flash.display::DisplayObject"/>
<accessor name="stage" access="readonly" type="flash.display::Stage" declaredBy="flash.display::DisplayObject"/>
<accessor name="mask" access="readwrite" type="flash.display::DisplayObject" declaredBy="flash.display::DisplayObject"/>
<accessor name="width" access="readwrite" type="Number" declaredBy="flash.display::DisplayObject"/>
<accessor name="visible" access="readwrite" type="Boolean" declaredBy="flash.display::DisplayObject"/>
<accessor name="alpha" access="readwrite" type="Number" declaredBy="flash.display::DisplayObject"/>
<accessor name="height" access="readwrite" type="Number" declaredBy="flash.display::DisplayObject"/>
<accessor name="mouseY" access="readonly" type="Number" declaredBy="flash.display::DisplayObject"/>
<accessor name="rotation" access="readwrite" type="Number" declaredBy="flash.display::DisplayObject"/>
<accessor name="mouseX" access="readonly" type="Number" declaredBy="flash.display::DisplayObject"/>
<accessor name="mouseEnabled" access="readwrite" type="Boolean" declaredBy="flash.display::InteractiveObject"/>
<accessor name="tabIndex" access="readwrite" type="int" declaredBy="flash.display::InteractiveObject"/>
<accessor name="doubleClickEnabled" access="readwrite" type="Boolean" declaredBy="flash.display::InteractiveObject"/>
<accessor name="focusRect" access="readwrite" type="Object" declaredBy="flash.display::InteractiveObject"/>
<accessor name="y" access="readwrite" type="Number" declaredBy="flash.display::DisplayObject"/>
<accessor name="cacheAsBitmap" access="readwrite" type="Boolean" declaredBy="flash.display::DisplayObject"/>
<accessor name="x" access="readwrite" type="Number" declaredBy="flash.display::DisplayObject"/>
<accessor name="opaqueBackground" access="readwrite" type="Object" declaredBy="flash.display::DisplayObject"/>
<accessor name="accessibilityImplementation" access="readwrite" type="flash.accessibility::AccessibilityImplementation" declaredBy="flash.display::InteractiveObject">
<metadata name="Inspectable">
<arg key="environment" value="none"/>
</metadata>
</accessor>
<accessor name="scrollRect" access="readwrite" type="flash.geom::Rectangle" declaredBy="flash.display::DisplayObject"/>
<accessor name="filters" access="readwrite" type="Array" declaredBy="flash.display::DisplayObject"/>
<accessor name="blendMode" access="readwrite" type="String" declaredBy="flash.display::DisplayObject"/>
<accessor name="transform" access="readwrite" type="flash.geom::Transform" declaredBy="flash.display::DisplayObject"/>
<accessor name="name" access="readwrite" type="String" declaredBy="flash.display::DisplayObject"/>
<accessor name="scale9Grid" access="readwrite" type="flash.geom::Rectangle" declaredBy="flash.display::DisplayObject"/>
<accessor name="loaderInfo" access="readonly" type="flash.display::LoaderInfo" declaredBy="flash.display::DisplayObject"/>
<accessor name="accessibilityProperties" access="readwrite" type="flash.accessibility::AccessibilityProperties" declaredBy="flash.display::DisplayObject"/>
<accessor name="contextMenu" access="readwrite" type="flash.ui::ContextMenu" declaredBy="flash.display::InteractiveObject"/>
<accessor name="soundTransform" access="readwrite" type="flash.media::SoundTransform" declaredBy="flash.display::Sprite"/>
<accessor name="parent" access="readonly" type="flash.display::DisplayObjectContainer" declaredBy="flash.display::DisplayObject"/>
<accessor name="numChildren" access="readonly" type="int" declaredBy="flash.display::DisplayObjectContainer"/>
<accessor name="dropTarget" access="readonly" type="flash.display::DisplayObject" declaredBy="flash.display::Sprite"/>
<accessor name="tabEnabled" access="readwrite" type="Boolean" declaredBy="flash.display::InteractiveObject"/>
<accessor name="hitArea" access="readwrite" type="flash.display::Sprite" declaredBy="flash.display::Sprite"/>
<accessor name="scaleX" access="readwrite" type="Number" declaredBy="flash.display::DisplayObject"/>
<accessor name="graphics" access="readonly" type="flash.display::Graphics" declaredBy="flash.display::Sprite"/>
<accessor name="scaleY" access="readwrite" type="Number" declaredBy="flash.display::DisplayObject"/>
<accessor name="textSnapshot" access="readonly" type="flash.text::TextSnapshot" declaredBy="flash.display::DisplayObjectContainer"/>
<accessor name="buttonMode" access="readwrite" type="Boolean" declaredBy="flash.display::Sprite"/>
<accessor name="tabChildren" access="readwrite" type="Boolean" declaredBy="flash.display::DisplayObjectContainer"/>
<accessor name="mouseChildren" access="readwrite" type="Boolean" declaredBy="flash.display::DisplayObjectContainer"/>
<method name="swapChildren" declaredBy="flash.display::DisplayObjectContainer" returnType="void">
<parameter index="1" type="flash.display::DisplayObject" optional="false"/>
<parameter index="2" type="flash.display::DisplayObject" optional="false"/>
</method>
<method name="startDrag" declaredBy="flash.display::Sprite" returnType="void">
<parameter index="1" type="Boolean" optional="true"/>
<parameter index="2" type="flash.geom::Rectangle" optional="true"/>
</method>
<method name="stopDrag" declaredBy="flash.display::Sprite" returnType="void"/>
<method name="removeEventListener" declaredBy="flash.events::EventDispatcher" returnType="void">
<parameter index="1" type="String" optional="false"/>
<parameter index="2" type="Function" optional="false"/>
<parameter index="3" type="Boolean" optional="true"/>
</method>
<method name="parseEmail_13_14_1115" declaredBy="describeType_Test" returnType="void"/>
<method name="addEventListener" declaredBy="flash.events::EventDispatcher" returnType="void">
<parameter index="1" type="String" optional="false"/>
<parameter index="2" type="Function" optional="false"/>
<parameter index="3" type="Boolean" optional="true"/>
<parameter index="4" type="int" optional="true"/>
<parameter index="5" type="Boolean" optional="true"/>
</method>
<method name="parseEmail_10_101_112" declaredBy="describeType_Test" returnType="void"/>
<method name="parseEmail_2" declaredBy="describeType_Test" returnType="void"/>
<method name="willTrigger" declaredBy="flash.events::EventDispatcher" returnType="Boolean">
<parameter index="1" type="String" optional="false"/>
</method>
<method name="dispatchEvent" declaredBy="flash.events::EventDispatcher" returnType="Boolean">
<parameter index="1" type="flash.events::Event" optional="false"/>
</method>
<method name="hasEventListener" declaredBy="flash.events::EventDispatcher" returnType="Boolean">
<parameter index="1" type="String" optional="false"/>
</method>
<method name="parseEmail_3" declaredBy="describeType_Test" returnType="void"/>
<method name="toString" declaredBy="flash.events::EventDispatcher" returnType="String"/>
<method name="parseEmail_1" declaredBy="describeType_Test" returnType="void"/>
<method name="globalToLocal" declaredBy="flash.display::DisplayObject" returnType="flash.geom::Point">
<parameter index="1" type="flash.geom::Point" optional="false"/>
</method>
<method name="localToGlobal" declaredBy="flash.display::DisplayObject" returnType="flash.geom::Point">
<parameter index="1" type="flash.geom::Point" optional="false"/>
</method>
<method name="getBounds" declaredBy="flash.display::DisplayObject" returnType="flash.geom::Rectangle">
<parameter index="1" type="flash.display::DisplayObject" optional="false"/>
</method>
<method name="addChildAt" declaredBy="flash.display::DisplayObjectContainer" returnType="flash.display::DisplayObject">
<parameter index="1" type="flash.display::DisplayObject" optional="false"/>
<parameter index="2" type="int" optional="false"/>
</method>
<method name="getRect" declaredBy="flash.display::DisplayObject" returnType="flash.geom::Rectangle">
<parameter index="1" type="flash.display::DisplayObject" optional="false"/>
</method>
<method name="removeChild" declaredBy="flash.display::DisplayObjectContainer" returnType="flash.display::DisplayObject">
<parameter index="1" type="flash.display::DisplayObject" optional="false"/>
</method>
<method name="addChild" declaredBy="flash.display::DisplayObjectContainer" returnType="flash.display::DisplayObject">
<parameter index="1" type="flash.display::DisplayObject" optional="false"/>
</method>
<method name="removeChildAt" declaredBy="flash.display::DisplayObjectContainer" returnType="flash.display::DisplayObject">
<parameter index="1" type="int" optional="false"/>
</method>
<method name="contains" declaredBy="flash.display::DisplayObjectContainer" returnType="Boolean">
<parameter index="1" type="flash.display::DisplayObject" optional="false"/>
</method>
<method name="hitTestObject" declaredBy="flash.display::DisplayObject" returnType="Boolean">
<parameter index="1" type="flash.display::DisplayObject" optional="false"/>
</method>
<method name="getChildIndex" declaredBy="flash.display::DisplayObjectContainer" returnType="int">
<parameter index="1" type="flash.display::DisplayObject" optional="false"/>
</method>
<method name="hitTestPoint" declaredBy="flash.display::DisplayObject" returnType="Boolean">
<parameter index="1" type="Number" optional="false"/>
<parameter index="2" type="Number" optional="false"/>
<parameter index="3" type="Boolean" optional="true"/>
</method>
<method name="setChildIndex" declaredBy="flash.display::DisplayObjectContainer" returnType="void">
<parameter index="1" type="flash.display::DisplayObject" optional="false"/>
<parameter index="2" type="int" optional="false"/>
</method>
<method name="getChildByName" declaredBy="flash.display::DisplayObjectContainer" returnType="flash.display::DisplayObject">
<parameter index="1" type="String" optional="false"/>
</method>
<method name="getChildAt" declaredBy="flash.display::DisplayObjectContainer" returnType="flash.display::DisplayObject">
<parameter index="1" type="int" optional="false"/>
</method>
<method name="parseEmail_4_5_6_7" declaredBy="describeType_Test" returnType="void"/>
<method name="getObjectsUnderPoint" declaredBy="flash.display::DisplayObjectContainer" returnType="Array">
<parameter index="1" type="flash.geom::Point" optional="false"/>
</method>
<method name="areInaccessibleObjectsUnderPoint" declaredBy="flash.display::DisplayObjectContainer" returnType="Boolean">
<parameter index="1" type="flash.geom::Point" optional="false"/>
</method>
<method name="swapChildrenAt" declaredBy="flash.display::DisplayObjectContainer" returnType="void">
<parameter index="1" type="int" optional="false"/>
<parameter index="2" type="int" optional="false"/>
</method>
</factory>
</type>
这样，只需要获取到该xml对象下的所有method节点，然后遍历它，匹配到包含该邮件格式id的方法，使用split将方法名分隔开：parseEmail、1、2、…，第一位则为方法名，之后的便是该方法可以解析的指定格式的id，调用this[funName](paras..);
as的示例代码：
package
{
import flash.display.Sprite;
import flash.utils.describeType;
import flash.utils.getDefinitionByName;
import flash.utils.getQualifiedClassName;
import flash.utils.getQualifiedSuperclassName;
public class describeType_Test extends Sprite
{
public function describeType_Test()
{
//this [object describeType_Test]
var clsStr:String = getQualifiedClassName(this); //describeType_Test
var supClsStr:String = getQualifiedSuperclassName(this); //flash.display::Sprite
var cls:Class = getDefinitionByName(clsStr) as Class;
var xml:XML = describeType(cls);
trace(xml);
}
public function parseEmail_1():void
{
}
public function parseEmail_2():void
{
}
public function parseEmail_3():void
{
}
public function parseEmail_4_5_6_7():void
{
}
public function parseEmail_10_101_112():void
{
}
public function parseEmail_13_14_1115():void
{
}
}
}