Package | Top Level |
Class | public dynamic class Class |
Inheritance | Class Object |
Language Version: | ActionScript 3.0 |
Runtime Versions: | Flash Player 9, AIR 1.0 |
new
operator.
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.
For example, if you are using an MXML compiler to generate SWF files, you would create an embedded class as follows:
[Embed(source="bratwurst.jpg")] public var imgClass:Class;
And, to instantiate it, you write the following:
var myImg:Bitmap = new imgClass();
See also
- Declare two classes as
ClassA
andClassB
. - Declare a variable of type Class named
classToConstruct
and one of type BooleanchooseClassA
, which is set totrue
in this case, but your code could use a custom test expression to set the value of that variable.
package { import flash.display.Sprite; public class ClassExample extends Sprite { public function ClassExample() { var classToConstruct:Class; var classInstance:Object; classToConstruct = ClassA; classInstance = new classToConstruct(); trace(classInstance); // [object ClassA] classToConstruct = ClassB; classInstance = new classToConstruct(); trace(classInstance); // [object ClassB] } } } class ClassA { } class ClassB { }
Fri Mar 19 2010, 02:45 AM -07:00