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

declaring it as abstract in the Component class makes sense. We can now draw the
whole snake.
Building the Composite Snake
Example 6-17 shows the updated constructor of the Main class from Example 6-14
that constructs the whole snake. Lines 10- 25 add the body segments to the snake in
black and gray alternating colors. Finally, the tail component is added in lines 26
through 28. The update( ) method is called once (line 30) to fit and display all components
on the stage as they’re initially placed offscreen (line 22). The completed
snake should look like Figure 6-6.
Example 6-17. Updated constructor in Main.as
1 public function Main( )
2 {
3 // create snake
4 snake = new Head( );
5 snake.x = snake.y = 200;
6
7 // add snake to stage
8 addChild(snake);
9
10 // add multiple body segments
11 var parentNode:Composite = snake;
12 var color:uint;
13 for (var i:uint = 0; i < 10; i++)
14 {
15 if (i % 2) {
16 color = 0x000000; // black
17 } else {
18 color = 0xC0C0C0; // grey
19 }
20 var segment:Composite = new BodySegment(color);
21 parentNode.add(segment);
22 segment.x = segment.y = -50; // place it off screen
23 addChild(segment);
24 parentNode = segment;
25 }
26 var tail:Component = new Tail( );
27 addChild(tail);
28 parentNode.add(tail); // add rattle
29
30 snake.update( ); // to fit the segments together
31
32 // register with the stage to receive key press events
33 stage.addEventListener(KeyboardEvent.KEY_DOWN, onKeyPress);
34 }
232 | Chapter 6: Composite Pattern