Class  - AS3

Package	Top Level
Class	public dynamic class Class
Inheritance	Class Object

Some methods, such as flash.net.getClassByAlias(), return an object of type Class. Other methods may have a parameter of type Class, such as flash.net.registerClassAlias().

The class name is the reference to the Class object, as this example shows:

 
 class Foo {
 }
 

The class Foo{} statement is the class definition that creates the Class object Foo. Additionally, the statement new Foo() will create a new instance of class Foo, and the result will be of type Foo.

Use the class statement to declare your classes. Class objects are useful for advanced techniques, such as assigning classes to an existing instance object at runtime, as shown in the "Examples" section below.

Any static properties and methods of a class live on the class's Class object. Class, itself, declares prototype.

Generally, you do not need to declare or create variables of type Class manually. However, in the following code, a class is assigned as a public Class property circleClass, and you can refer to this Class property as a property of the main Library class:

 package {
  import flash.display.Sprite;
  public class Library extends Sprite {
      
      public var circleClass:Class = Circle;
      public function Library() {
      }
  }
 }
  
 import flash.display.Shape;
 class Circle extends Shape {
  public function Circle(color:uint = 0xFFCC00, radius:Number = 10) {
      graphics.beginFill(color);
      graphics.drawCircle(radius, radius, radius);
  }
 }
 

Another SWF file can load the resulting Library.swf file and then instantiate objects of type Circle. The following example shows one way to get access to a child SWF file's assets. (Other techniques include using flash.utils.getDefnitionByName() or importing stub definitions of the child SWF file.)

 package {
  import flash.display.Sprite;
  import flash.display.Shape;
  import flash.display.Loader;
  import flash.net.URLRequest;
  import flash.events.Event;
  public class LibaryLoader extends Sprite {
      public function LibaryLoader() {
          var ldr:Loader = new Loader();
          var urlReq:URLRequest = new URLRequest("Library.swf");
          ldr.load(urlReq);
          ldr.contentLoaderInfo.addEventListener(Event.COMPLETE, loaded);
      }
      private function loaded(event:Event):void {
          var library:Object = event.target.content;
          var circle:Shape = new library.circleClass();
          addChild(circle);
      }
  }
 }
 

In ActionScript 3.0, you can create embedded classes for external assets (such as images, sounds, or fonts) that are compiled into SWF files. In earlier versions of ActionScript, you associated those assets using a linkage ID with the MovieClip.attachMovie() method. In ActionScript 3.0, each embedded asset is represented by a unique embedded asset class. Therefore, you can use the new operator to instantiate the asset's associated class and call methods and properties on that asset.

View the examples

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