Say hello to my little friend - describeType()

By scott

It amazes me that people don’t know about describeType(). If you’re lazy, or as some developers call it, efficient, you always don’t have time, or really don’t feel like digging through half assed completed documentation to see what parameters a classes constructor accepts. Sounds like the perfect time to combine forces, trace() meet flash.utils.describeType(). The describeType() method returns an xml dump that contains all the details you’d ever need to know about any object that is passed in as a parameter.For example, let’s pretend this is our first time working with Flash (of course you could be working in Flex too), lucky us, we never had to use AS2 or AS1, we only heard our cubicle neighbors groaning about spaghetti code, and hidden code attached to buttons. Since this is our first time using Flash we don’t even know what a MovieClip is or what methods are available to us. One simple line of code will solve our ignorance.

trace(flash.utils.describeType(flash.display.MovieClip));

This one little line of code returns this to us in our output window (shortened for your scroll wheels sake):

<type name="flash.display::MovieClip" base="Class" isDynamic="true" isFinal="true" isStatic="true">  <extendsClass type="Class"/>  <extendsClass type="Object"/>  <accessor name="prototype" access="readonly" type="*" declaredBy="Class"/>  <factory type="flash.display::MovieClip">    <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.display::IBitmapDrawable"/>    <implementsInterface type="flash.events::IEventDispatcher"/>    <accessor name="scenes" access="readonly" type="Array" declaredBy="flash.display::MovieClip"/>    <method name="stop" declaredBy="flash.display::MovieClip" returnType="void"/>    <method name="nextScene" declaredBy="flash.display::MovieClip" returnType="void"/>    <method name="play" declaredBy="flash.display::MovieClip" returnType="void"/>    <accessor name="currentScene" access="readonly" type="flash.display::Scene" declaredBy="flash.display::MovieClip"/>    <accessor name="currentFrame" access="readonly" type="int" declaredBy="flash.display::MovieClip"/>    <accessor name="trackAsMenu" access="readwrite" type="Boolean" declaredBy="flash.display::MovieClip"/>    <method name="gotoAndStop" declaredBy="flash.display::MovieClip" returnType="void">      <parameter index="1" type="Object" optional="false"/>      <parameter index="2" type="String" optional="true"/>    </method>    <accessor name="currentLabels" access="readonly" type="Array" declaredBy="flash.display::MovieClip"/>    <method name="willTrigger" declaredBy="flash.events::EventDispatcher" returnType="Boolean">      <parameter index="1" type="String" optional="false"/>    </method>  </factory></type>

The output window never looked so good. Methods, paramaters, superclasses, accessors, the amount of information that is returned is beautiful. I don’t know how many for in loops I wrote in AS2 just to try and figure out what methods were available in a custom class.One thing to note is that describeType() only shows public properties and methods, and will not show properties and methods that are private, package internal or in custom namespaces.If you have never looked at the flash.utils.* package, I suggest you do, there are some handy little utilities in there.