ActionScript 3.0 Design Patterns.pdf - VideoTutorials-bg.com

Example 6-27. MainWing.as with modifiedMainWing class
1 package
2 {
3 import flash.events.*;
4
5 public class MainWing extends Composite
6 {
7 public function MainWing(weight:Number, damage:Number = 0)
8 {
9 graphics.lineStyle(25, 0x999999);
10 graphics.moveTo(0, 0);
11 graphics.lineTo(100, 0);
12
13 addEventListener(MouseEvent.CLICK, doDamage);
14
15 super(weight, damage);
16 }
17
18 private function doDamage(evt:Event)
19 {
20 this.nDamage += 20;
21 trace('Damage to this wing is now ' + this.nDamage);
22 if (this.nDamage > 50)
23 {
24 trace('Wing detached from fuselage - fatal crash!');
25 parent.removeChild(this);
26 }
27 evt.stopPropagation( );
28 // stop event propegation to subsequent nodes
29 }
30 }
31 }
Example 6-27 shows the modified MainWing class. Note the conditional statement in
lines 22- 26. If the damage exceeds 50, this node removes itself from the display list
(and the airplane composite structure) by calling removeChild in its parent. Before we
can test our modified components, a few changes to the Main class are necessary to
display total damage.
Calculating Total Damage to the Airplane
In the interests of keeping the example simple, we will register a mouse click handler
called showDamage to the stage to display the total damage to the airplane. The following
statement needs to be added at the end of the constructor in the Main class shown
in Example 6-25.
stage.addEventListener(MouseEvent.CLICK, showDamage);
In addition, the following showDamage event handler method should be added to the
Main class as well.
242 | Chapter 6: Composite Pattern