Flash / Flex / ActionScript/Class/Inheritance

Add new method to the children class

   <source lang="java">

package{

 import flash.display.Sprite;
 
 public class Main extends Sprite{
   public function Main(){
       var bInstance = new B(  );
       bInstance.m();       // Displays: Method m(  ) was called
       bInstance.n();       // Displays: Method n(  ) was called
       trace(bInstance.v);  // Displays: 10

   }
 }

} class A {

 public var v = 10;
 public function m (  ) {
   trace("Method m(  ) was called");
 }

} class B extends A {

 public function n (  ) {
   trace("Method n(  ) was called");
 }

} Method m( ) was called Method n( ) was called 10

       </source>
   
  

A Primer on Inheritance

   <source lang="java">

package{

 import flash.display.Sprite;
 
 public class Main extends Sprite{
   public function Main(){

       var aInstance = new A(  );
       aInstance.m();       // Displays: Method m(  ) was called
       trace(aInstance.v);  // Displays: 10
       var bInstance:B = new B(  );
       bInstance.m();       // Displays: Method m(  ) was called
       trace(bInstance.v);  // Displays: 10
       
   }
 }

} class A {

 public var v = 10;
 public function m (  ) {
   trace("Method m(  ) was called");
 }

} class B extends A { } Method m( ) was called 10 Method m( ) was called 10

       </source>
   
  

Call super constructor with parameter

   <source lang="java">

package{

 import flash.display.Sprite;
 
 public class Main extends Sprite{
   public function Main(){

   }
 }

} class Ball {

 private var r;
 public function Ball (radius) {
   r = radius;
 }

}

class ColoredBall extends Ball {

 private var c;
 public function ColoredBall (radius, color) {
   super(radius);
   c = color;
 }

}

       </source>
   
  

Class Scope: Code placed at the top-level of a class body resides in that class"s scope.

   <source lang="java">

package {

 public class SomeClass {
   // Code here is in the someClass scope
 }

} package {

 public class SomeClass extends SomeParentClass {
 }

} package {

 public class SomeParentClass {
 }

}

       </source>
   
  

Constructor Methods in Subclasses

   <source lang="java">

package{

 import flash.display.Sprite;
 
 public class Main extends Sprite{
   public function Main(){

   }
 }

} class A {

 public function A (  ) {
 }

} class B extends A {

 public function B (  ) {
   // Invoke superclass"s constructor method
   super(  );
 }

}

       </source>
   
  

Extends the super class

   <source lang="java">

/* class ClassName extends SuperClassName {

 // Class definition goes here.

}

• /

package{

 import flash.display.Sprite;
 
 public class Main extends Sprite{
   public function Main(){
       var rBunny:Rabbit = new Rabbit("William", "White and Brown");
       
       trace(rBunny.name);  // Displays: William
       trace(rBunny.coloration);  // Dislays: White and Brown
   }
 }

} class Mammal {

 var _sName:String;
 public function get name():String {
   return _sName;
 }
 public function set name(sName:String):void {
   _sName = sName;
 }

} class Rabbit extends Mammal {

 public var _sColoration:String;
 public function Rabbit(sName:String, sColoration:String) {
   _sName = sName;
   _sColoration = sColoration;
 }
 public function get coloration():String {
   return _sColoration;
 }

}

       </source>
   
  

If a subclass does not define a constructor, ActionScript automatically creates one and adds a super call as its only statement.

   <source lang="java">

class B extends A {

 public function B (  ) {
   super(  );
 }

} class B extends A { }

class Rectangle {

 protected var w = 0;
 protected var h = 0;
 public function Rectangle (width, height) {
   setSize(width, height);
 }
 public function setSize (newW, newH) {
   w = newW;
   h = newH;
 }
 public function getArea (  ) {
   return w * h;
 }

} class Square extends Rectangle {

 public function Square (side) {
   super(side, side);
 }
 override public function setSize (newW, newH) {
   if (newW == newH) {
     super.setSize(newW, newH);
   }
 }

}

       </source>
   
  

Static Methods and Static Variables Not Inherited

   <source lang="java">

package{

 import flash.display.Sprite;
 
 public class Main extends Sprite{
   public function Main(){
       var bInstance = new B(  );
       bInstance.s(); // Error
   }
 }

} class A {

 public static function s (  ) {
   trace("A.s(  ) was called");
 }

} class B extends A {

 public function B (  ) {
 }

}

       </source>
   
  

Three-level inheritance

   <source lang="java">

package{

 import flash.display.Sprite;
 
 public class Main extends Sprite{
   public function Main(){
       var cInstance = new C(  );
       cInstance.m();  // Displays: Method m(  ) was called
       cInstance.n();  // Displays: Method n(  ) was called
       cInstance.o();  // Displays: Method o(  ) was called
       trace(cInstance.v);  // Displays: 10
   }
 }

} class A {

 public var v = 10;
 public function m (  ) {
   trace("Method m(  ) was called");
 }

} class B extends A {

 public function n (  ) {
   trace("Method n(  ) was called");
 }

} class C extends B {

 public function o (  ) {
   trace("Method o(  ) was called");
 }

}

       </source>
   
  

You can call the superclass implementation from the subclass implementation using the super keyword to reference the superclass:

   <source lang="java">

   class Superclass {
       public function Superclass(  ) {}
       public function toString(  ):String {
           return "Superclass.toString(  )";
       }
   }
   class Subclass extends Superclass {
       public function Subclass(  ) {}
       override public function toString(  ):String {
           super.toString();
           return "Subclass.toString(  )";
       }
   }
       </source>