MACROMEDIA FLEX-FLEX ACTIONSCRIPT LANGUAGE Reference page 154

The following example shows a second AS file, called Car.as, in the same directory. This class
extends the Vehicle class, modifying it in three ways. First, the Car class adds a variable
fullSizeSpare
method specific to cars,
overrides the
stop()
to stop.
class Car extends Vehicle {
var fullSizeSpare:Boolean;
function Car(param_numDoors:Number, param_color:String,
param_fullSizeSpare:Boolean) {
this.numDoors = param_numDoors;
this.color = param_color;
this.fullSizeSpare = param_fullSizeSpare;
}
function activateCarAlarm():Void {
trace("[Car] activateCarAlarm");
}
function stop():Void {
trace("[Car] stop with anti-lock brakes");
}
}
The following example instantiates a Car object, calls a method defined in the Vehicle class
( ), then calls the method overridden by the Car class (
start()
from the Car class (
var myNewCar:Car = new Car(2, "Red", true);
myNewCar.start(); // output: [Vehicle] start
myNewCar.stop(); // output: [Car] stop with anti-lock brakes
myNewCar.activateCarAlarm(); // output: [Car] activateCarAlarm
A subclass of the Vehicle class can also be written using the keyword
can use to access properties and methods of the superclass. The following example shows a third
AS file, called Truck.as, again in the same directory. The Truck class uses the
the constructor and again in the overridden
class Truck extends Vehicle {
var numWheels:Number;
function Truck(param_numDoors:Number, param_color:String,
param_numWheels:Number) {
super(param_numDoors, param_color);
this.numWheels = param_numWheels;
}
function reverse():Void {
beep();
super.reverse();
}
function beep():Void {
trace("[Truck] make beeping sound");
}
}
154 Chapter 5: ActionScript Core Language Elements
to track whether the car object has a full-size spare tire. Second, it adds a new
activateCarAlarm()
function to add the fact that the Car class uses an anti-lock braking system
activateCarAlarm()
, that activates the car's anti-theft alarm. Third, it
stop()
):
function.
reverse()
), and finally calls a method
, which the subclass
super
keyword in
super