Advanced ActionScript 3: Design Patterns, Second Edition (2015)

Chapter 9. Q&A

The previous chapters on design patterns have covered an enormous amount, and now you get an opportunity to use that information. This chapter provides a quiz consisting of 25 questions, to provide you with immediate feedback on your understanding of the material. These questions pertain to design patterns (creational, behavioral and structural) as covered in this book.

You won’t be scored or judged on your answers, so do your best to use this chapter as a way to further understand and practice using design patterns.

Notes: 1. For formatting reasons, the quiz questions don’t include packages. External definitions must always have a package keyword. 2. Some questions are straightforward, and others require you to supply the implementations for incomplete listings.

Design Pattern Quiz

1. The common prefixes make, create, and get reflect which specific design pattern?

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2. Primitive operations, which are prefixed with do, are used by which pattern?

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3. Separate the instantiation from its assembly to promote flexibility in Listing 9-1.

Listing 9-1. AbstractClass

public class AbstractClass extends Sprite
{
public function AbstractClass()
{
var someMovieClip : MovieClip = new ConcreteMovieClip();
someMovieClip.y = 25;
someMovieClip.x = 40;
someMovieClip.play();
addChild( someMovieClip );
}
}

Listing 9-2. AbstractClass

Listing 9-3. FactoryMethodClass.as

4. Design a decorator that enhances a bitmap with a scrollRect that can scroll to reveal concealed areas of the image using the mouse. The bitmap interface is IBitmap in Listing 9-4.

Listing 9-4. IBitmap

public interface IBitmap
{
function get bitmapData() : BitmapData;
function set bitmapData( value : BitmapData ) : void;
function get pixelSnapping() : String;
function set pixelSnapping( value : String ) : void;
function get smoothing() : Boolean;
function set smoothing( value : Boolean ) : void;
}

Listing 9-5. DecoratorAbstract.as

Listing 9-6. MouseScrollingDecorator.as

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protected var _viewport : Rectangle;
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protected var _pixelsPerWide : int;
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protected var _pixelsPerTall : int;
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private var _rectTall : int = 400;
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private var _rectWide : int = 400;
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5. Explain how you can subclass a method and provide it with an implementation without disturbing the algorithm in which the implementation is required.

6. Explain the benefits of an Iterator in an aggregate.

7. Define a component interface that favors transparency over safety in all of its components.

Listing 9-7. IComponent.as

8. This pattern ensures state synchronization. ____________________

9. Mushroomy Kingdom uses the console platform and its power to revisit stage 1-1 with dreamy textures. Table 9-1 lists the names that reference the linked images of the .fla.

Table 9-1. Stage 1-1 concretes revisited

New stone floor tile: StoneFlooring

New money box tile: MoneyBox

New brick tile: WhiteStone

New pipe tile: IndustrialPlumbing

Cloud: AlphaCloud

Hill terrain: HillSide

Using the AbstractMarioLevelDirector and the AbstractMarioEsqueLevelEditor code and the reference names from Table 9-1, write the implementations to populate this scene. The dimensions aren’t important.

Listing 9-8. AbstractMarioEsqueLevelEditor.as

public class AbstractMarioEsqueLevelEditor
{
private var _bitmapD : BitmapData;
private var _backgroundColor : uint;
private var _width : int;
private var _height : int;
private var _pt : Point;
private var _tile : Shape;

public function AbstractMarioEsqueLevelEditor()
{
_tile = new Shape();
_pt = new Point( 0 , 0 );
}

final public function createMap() : void
{
bitmap = doCreateMap();
}

final public function getLevel() : BitmapData
{
return _bitmapD;
}

final public function createStone( rect : Rectangle ) : void
{
addTile( doCreateStone() , rect );
}

final public function createSolidBrick( rect : Rectangle ) : void
{
addTile( doCreateSolidBrick() , rect );
}

final public function createBreakableBrick( rect : Rectangle ) : void
{
addTile( doCreateBreakableBrick() , rect );
}

final public function createMoneyBox( rect : Rectangle ) : void
{
addTile( doCreateMoneyBox() , rect );
}

final public function createCloud( rect : Rectangle ) : void
{
addTile( doCreateCloud() , rect );
}

final public function createHill( rect : Rectangle ) : void
{
addTile( doCreateHill() , rect );
}

final public function createBush( rect : Rectangle ) : void
{
addTile( doCreateBush() , rect );
}

final public function createCastle( rect : Rectangle ) : void
{
addTile( doCreateCastle() , rect );
}

final public function createPipe( rect : Rectangle ) : void
{
addTile( doCreatePipe() , rect );
}

final public function get width() : int
{
return _width;
}

final public function set width( width : int ) : void
{
_width = width;
}

final public function get height() : int
{
return _height;
}

final public function set height( height : int ) : void
{
_height = height;
}

final public function get backgroundColor() : uint
{
return _backgroundColor;
}

final public function set backgroundColor( backgroundColor : uint ) : void
{
_backgroundColor = backgroundColor;
}

final public function get bitmap() : BitmapData
{
return _bitmapD;
}

final public function set bitmap( bitmap : BitmapData ) : void
{
_bitmapD = bitmap;
}

protected function doCreateMap() : BitmapData
{
return new BitmapData( width , height , false , backgroundColor );
}

protected function doCreateStone() : DisplayObject
{
throw new IllegalOperationError( 'doCreateStone must be overridden' );
return null;
}

protected function doCreateSolidBrick() : DisplayObject
{
throw new IllegalOperationError( 'doCreateSolidBrick must be overridden' );
return null;
}

protected function doCreateBreakableBrick() : DisplayObject
{
throw new IllegalOperationError( 'doCreateBreakableBrick must be overridden' );
return null;
}

protected function doCreateMoneyBox() : DisplayObject
{
throw new IllegalOperationError( 'doCreateMoneyBox must be overridden' );
return null;
}

protected function doCreateCloud() : DisplayObject
{
throw new IllegalOperationError( 'doCreateCloud must be overridden' );
return null;
}

protected function doCreateHill() : DisplayObject
{
throw new IllegalOperationError( 'doCreateHill must be overridden' );
return null;
}

protected function doCreateBush() : DisplayObject
{
throw new IllegalOperationError( 'doCreateBush must be overridden' );
return null;
}

protected function doCreateCastle() : DisplayObject
{
throw new IllegalOperationError( 'doCreateCastle must be overridden' );
return null;
}

protected function doCreatePipe() : DisplayObject
{
throw new IllegalOperationError( 'doCreatePipe must be overridden' );
return null;
}

private function addTile( dO : DisplayObject , rect : Rectangle ) : void
{
var sprite : BitmapData = snapShot( dO );
_pt.x = rect.x;
_pt.y = rect.y;
if (rect.width > 0 || rect.height > 0)
{
sprite = tile( sprite , rect );
}
bitmap.copyPixels( sprite , sprite.rect , _pt );
}

private function snapShot( dO : DisplayObject ) : BitmapData
{
var snapshot : BitmapData = new BitmapData( dO.width , dO.height , true , 0 );
snapshot.draw( dO );
return snapshot;
}

private function tile( bmpd : BitmapData , rect : Rectangle ) : BitmapData
{
var _t : Shape = _tile;
var g : Graphics = _t.graphics;
g.clear();
g.beginBitmapFill( bmpd , null , true , false );
g.drawRect( 0 , 0 , rect.width , rect.height );
g.endFill();
return snapShot( _t );
}
}

Listing 9-9. QuizLevelEditor.as

Listing 9-10. AbstractMarioLevelDirector.as

public class AbstractMarioLevelDirector
{
protected const _width : int = 400;
protected const _height : int = 300;
protected const _bgColor : uint = 0xacccff;
protected var _builder : AbstractMarioEsqueLevelEditor;

public function AbstractMarioLevelDirector( builder:AbstractMarioEsqueLevelEditor );
{
_builder = builder;
}
public function getLevel() : BitmapData
{
return _builder.getLevel();
}
}

Listing 9-11. QuizLevelDirector.as

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10.Explain why it’s unwise to use a Simple Singleton in an application.

11.The following code is from an unrevealed class.

Listing 9-12. Unrevealed class

...cont
public function makeFastFoodSandwich( menu_number : int ) : ValueMeal
{
switch(menu_number)
{
case 1:
return new DoubleStack();
break;
case 2 :
return new ChickenSandwich();
break;
case 3:
return new ChickenNuggets();
break;
case 4:
return new Frosty();
break;
}
}
...cont

The code in Listing 9-12 uses the Factory Method pattern? True False

12.Twitter is the epitome of which design pattern? ____________________

13.Having parallel hierarchies means you use fewer classes than when using orthogonal hierarchies. True False

14.These three patterns can optionally intercept a request before passing it on.

____________________
____________________
____________________

15.Show a loose composite that stops all MovieClips in the DisplayList.

//traverse(this.stage);
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16.Re-create the display list from AS3 as a composite.

Listing 9-13. IComponent.as (DisplayObject) interface

Listing 9-14. IComposite.as (DisplayObjectContainer) interface

Listing 9-15. Leaf.as (DisplayObject)

public class Leaf implements __________________
{
}

17.What are the two most significant differences between the State pattern and the Strategy pattern?

18.Suppose a loader uses the following states: Closed, OpeningConnection, Loading, and Loaded. Given the interface of ILoader shown in Listing 9-16, assemble a loader using only the State pattern, ensuring that the loader can load a new request at any given point in time, as well as be destroyed, without using any conditional statements.

Listing 9-16. Loader interface

public interface ILoader
{
function close();

function load( request : URLRequest , context : LoaderContext = null ) : void;

function loadBytes( bytes : ByteArray , context : LoaderContext = null ) : void;

function get content() : DisplayObject;

function get contentLoaderInfo() : LoaderInfo;

function get ldr() : Loader;

function dispose() : void;
}

Listing 9-17. AbstractLoadersContext.as

public class AbstractLoadersContext extends Sprite implements ILoader
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{
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private var _ldr : Loader;
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protected var _stateLoader : ALoaderStateObject;
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public function AbstractLoadersContext()
_______________________________________________________________
{
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addChild( _ldr = new Loader() );
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_stateLoader = createState( this );
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}
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Listing 9-18. LoadersContext.as

Listing 9-19. ALoaderStateObject.as extends Object

Listing 9-20. EmptyLoaderStateObject.as extends ALoaderStateObject

Listing 9-21. OpeningConnectionStateObject.as extends ALoaderStateObject
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Listing 9-22. LoadingStateObject.as extends ALoaderStateObject
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Listing 9-23. LoadedStateObject.as extends ALoaderStateObject

19.Write an AbstractShape class and its subclasses, Square and Circle, so they can be drawn and cleared. Additionally, construct an AbstractCommand class that can execute and un-do said executed code. There are two possible solutions; write both.

Listing 9-24. IGraphics.as interface

Listing 9-25. AbstractShape.as constants WIDE and TALL are both 20 pixels. FILL_COLOR is yellow.

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protected const WIDE : int = 20;
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protected const TALL : int = 20;
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private const FILL_COLOR : uint = 0xfff000;
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Listing 9-26. CircleShape.as

Listing 9-27. SquareShape.as

Listing 9-28. AbstractShapeCommand.as

Listing 9-29. ShapeCommandDraw.as

Listing 9-30. ShapeCommandUndo.as

Listing 9-31. AbstractShapeUndoCommand.as

Listing 9-32. ShapeCommandWithUndo.as

20.The Execute method accompanies which design pattern?

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21.Explain the advantage of the Abstract Factory pattern over the Factory Method pattern.

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22.In ActionScript 3.0, what are the three design patterns used in the EventSystem to carry out events of DisplayObjects?

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23.Three objects make up an image loader in an application: a loader, an image mask, and a description box. Using these three objects, the sequence must occur in the following order:

An image loads.

The mask transitions to reveal the image.

Text appears, giving a description.

Demonstrate how the Chain of Responsibility pattern can properly compliment the output of the following client code in Listing 9-33.

Listing 9-33. DocumentClass using the Chain of Responsibility pattern to accomplish its sequence

public function DocumentClass()
{
var img : AbstractView = new ImageView();

var mask : AbstractView = new MaskView();
img.addHandler( mask );

var tf : AbstractView = new TextFieldView();
mask.addHandler( tf );

tf.addHandler( IHandler( new NullHandler() ) );
}
//... [object ImageView] target hit;
//... [object MaskView] target hit;
//... [object TextFieldView] target hit;
//... [object NullHandler] target hit: end of Chain;

Listing 9-34. IHandler interface

Listing 9-35. AbstractView

Listing 9-36. ImageView.as loads the following image: www.spilled-milk.com/000.jpg.

Listing 9-37. MaskView

Listing 9-38. DescriptionView

24.What pattern decouples multiple subsystems from client messaging by funneling those implementations into a simpler interface? The façade pattern

25.Choose the appropriate associations.

Model	Composite pattern
View	Subject pattern
Controller	Observer pattern
	Strategy pattern

Answers to Design Patterns Quiz

1. The common prefixes make, create, and get reflect which specific design pattern?

The Factory Method pattern

2. Primitive operations, which are prefixed with do, are used by which pattern?

The Template Method pattern

3. Separate the instantiation from its assembly to promote flexibility in Listing 9-1.

Listing 9-1. AbstractClass

public class AbstractClass extends Sprite
{
public function AbstractClass()
{
var someMovieClip : MovieClip = new ConcreteMovieClip();
someMovieClip.y = 25;
someMovieClip.x = 40;
someMovieClip.play();
addChild( someMovieClip );
}
}

Listing 9-2. AbstractClass
public class AbstractClass extends Sprite

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{
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public function AbstractClass ()
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{
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var mc : MovieClip = createMovie();
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mc.y = 25;
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mc.x = 40;
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mc.play();
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addChild( mc );
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}
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protected function createMovie() : MovieClip
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{
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throw new IllegalOperationError( 'createMovie must be overridden' );
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return null;
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}
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}
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Listing 9-3. FactoryMethodClass.as

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public class FactoryMethodClass extends AbstractClass
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{
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override protected function createMovie() : MovieClip
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{
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return new ConcreteMovieClip();
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}
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}
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4. Design a decorator that enhances a bitmap with a scrollRect that can scroll to reveal concealed areas of the image using the mouse. The bitmap interface is IBitmap in Listing 9-4.

Listing 9-4. IBitmap

Listing 9-5. DecoratorAbstract.as

public class DecoratorAbstract extends Sprite implements IBitmap
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{
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protected var _decoratee : Bitmap;
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public function DecoratorAbstract( decoratee : Bitmap ) : void
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{
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_decoratee = decoratee;
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addChild( decoratee );
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}
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public function get bitmapData() : BitmapData
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{
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return _decoratee.bitmapData;
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}
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public function set bitmapData( value : BitmapData ) : void
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{
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_decoratee.bitmapData = value;
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}
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public function get pixelSnapping() : String
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{
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return _decoratee.pixelSnapping;
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}
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public function set pixelSnapping( value : String ) : void
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{
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_decoratee.pixelSnapping = value;
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}
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public function get smoothing() : Boolean
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{
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return _decoratee.smoothing;
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}
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public function set smoothing( value : Boolean ) : void
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{
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_decoratee.smoothing = value;
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}
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}
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Listing 9-6. MouseScrollingDecorator.as

public class MouseScrollingDecorator extends DecoratorAbstract
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{
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protected var _viewport : Rectangle;
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protected var _pixelsPerWide : int;
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protected var _pixelsPerTall : int;
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private var _rectTall : int = 400;
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private var _rectWide : int = 400;
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public function MouseScrollingDecorator( bitmap : Bitmap )
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{
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super( bitmap );
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addEventListener( MouseEvent.MOUSE_MOVE , onMovement );
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_decoratee.scrollRect = new Rectangle( 0 , 0 , _rectWide , _rectTall );
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_pixelsPerWide = bitmap.width / _rectWide;
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_pixelsPerTall = bitmap.height / _rectTall;
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cacheAsBitmap = true;
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}
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private function onMovement( event : MouseEvent ) : void
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{
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var localRect : Rectangle = this._decoratee.scrollRect;
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localRect.x = event.localX * _pixelsPerWide;
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localRect.y = event.localY;
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_decoratee.scrollRect = localRect;
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}
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}
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5. Explain how you can subclass a method and provide it with an implementation without disturbing the algorithm in which the implementation is required.

The Template Method pattern offers the solution by marking the as final the method that defines the primitive operations that make up an algorithm. The primitive operations reveal hooks for which a subclass can provide implementations, while protecting the default implementation of the superclass.

6. Explain the benefits of an Iterator and an aggregate.

Using an iterator along with an aggregate conceals the logic that necessitates element retrieval from the aggregate, which would otherwise pollute a client with unnecessary details.

7. Define a component interface that favors transparency over safety in all of its components and leaves.

Listing 9-7. IComponent.as
public interface IComponent

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{
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function addComponent( cmpt : Component ) : void;
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function removeComponent( cmpt : Component ) : void;
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function operation() : void;
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}
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8. This pattern ensures state synchronization. The Observer pattern

9. Mushroomy Kingdom uses the console platform and its power to revisit stage 1-1 with dreamy textures. Table 9-1 lists the names that reference the linked images of the .fla.

Table 9-1. Stage 1-1 concretes revisited

New stone floor tile: StoneFlooring

New money box tile: MoneyBox

New brick tile: WhiteStone

New pipe tile: IndustrialPlumbing

Cloud: AlphaCloud

Hill terrain: HillSide

Using the AbstractMarioLevelDirector.as and the AbstractMarioEsqueLevelEditor.as code and the reference names from Table 9-1, write the implementations to populate this scene. The dimensions aren’t important.

Listing 9-8. AbstractMarioEsqueLevelEditor.as

public class AbstractMarioEsqueLevelEditor
{
private var _bitmapD : BitmapData;
private var _backgroundColor : uint;
private var _width : int;
private var _height : int;
private var _pt : Point;
private var _tile : Shape;

public function AbstractMarioEsqueLevelEditor()
{
_tile = new Shape();
_pt = new Point( 0 , 0 );
}

final public function createMap() : void
{
bitmap = doCreateMap();
}

final public function getLevel() : BitmapData
{
return _bitmapD;
}

final public function createStone( rect : Rectangle ) : void
{
addTile( doCreateStone() , rect );
}

final public function createSolidBrick( rect : Rectangle ) : void
{
addTile( doCreateSolidBrick() , rect );
}

final public function createBreakableBrick( rect : Rectangle ) : void
{
addTile( doCreateBreakableBrick() , rect );
}

final public function createMoneyBox( rect : Rectangle ) : void
{
addTile( doCreateMoneyBox() , rect );
}

final public function createCloud( rect : Rectangle ) : void
{
addTile( doCreateCloud() , rect );
}

final public function createHill( rect : Rectangle ) : void
{
addTile( doCreateHill() , rect );
}

final public function createBush( rect : Rectangle ) : void
{
addTile( doCreateBush() , rect );
}

final public function createCastle( rect : Rectangle ) : void
{
addTile( doCreateCastle() , rect );
}

final public function createPipe( rect : Rectangle ) : void
{
addTile( doCreatePipe() , rect );
}

final public function get width() : int
{
return _width;
}

final public function set width( width : int ) : void
{
_width = width;
}

final public function get height() : int
{
return _height;
}

final public function set height( height : int ) : void
{
_height = height;
}

final public function get backgroundColor() : uint
{
return _backgroundColor;
}

final public function set backgroundColor( backgroundColor : uint ) : void
{
_backgroundColor = backgroundColor;
}

final public function get bitmap() : BitmapData
{
return _bitmapD;
}

final public function set bitmap( bitmap : BitmapData ) : void
{
_bitmapD = bitmap;
}

protected function doCreateMap() : BitmapData
{
return new BitmapData( width , height , false , backgroundColor );
}

protected function doCreateStone() : DisplayObject
{
throw new IllegalOperationError( 'doCreateStone must be overridden' );
return null;
}

protected function doCreateSolidBrick() : DisplayObject
{
throw new IllegalOperationError( 'doCreateSolidBrick must be overridden' );
return null;
}

protected function doCreateBreakableBrick() : DisplayObject
{
throw new IllegalOperationError('doCreateBreakableBrick must be
overridden');
return null;
}

protected function doCreateMoneyBox() : DisplayObject
{
throw new IllegalOperationError( 'doCreateMoneyBox must be overridden' );
return null;
}

protected function doCreateCloud() : DisplayObject
{
throw new IllegalOperationError( 'doCreateCloud must be overridden' );
return null;
}

protected function doCreateHill() : DisplayObject
{
throw new IllegalOperationError( 'doCreateHill must be overridden' );
return null;
}

protected function doCreateBush() : DisplayObject
{
throw new IllegalOperationError( 'doCreateBush must be overridden' );
return null;
}

protected function doCreateCastle() : DisplayObject
{
throw new IllegalOperationError( 'doCreateCastle must be overridden' );
return null;
}

protected function doCreatePipe() : DisplayObject
{
throw new IllegalOperationError( 'doCreatePipe must be overridden' );
return null;
}

private function addTile( dO : DisplayObject , rect : Rectangle ) : void
{
var sprite : BitmapData = snapShot( dO );
_pt.x = rect.x;
_pt.y = rect.y;
if (rect.width > 0 || rect.height > 0)
{
sprite = tile( sprite , rect );
}
bitmap.copyPixels( sprite , sprite.rect , _pt );
}

private function snapShot( dO : DisplayObject ) : BitmapData
{
var snapshot : BitmapData = new BitmapData( dO.width, dO.height , true , 0 );
snapshot.draw( dO );
return snapshot;
}

private function tile( bmpd : BitmapData , rect : Rectangle ) : BitmapData
{
var _t : Shape = _tile;
var g : Graphics = _t.graphics;
g.clear();
g.beginBitmapFill( bmpd , null , true , false );
g.drawRect( 0 , 0 , rect.width , rect.height );
g.endFill();
return snapShot( _t );
}
}

Listing 9-9. QuizLevelEditor.as

public class QuizLevelEditor extends AbstractMarioEsqueLevelEditor
___________________________________________________________________
{
___________________________________________________________________
public function QuizLevelEditor()
___________________________________________________________________
{
___________________________________________________________________
super();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override protected function doCreateMap() : BitmapData
___________________________________________________________________
{
___________________________________________________________________
return new BitmapData( width , height , false , backgroundColor );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override protected function doCreateStone() : BitmapData
___________________________________________________________________
{
___________________________________________________________________
return new Stone();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override protected function doCreateSolidBrick() : DisplayObject
___________________________________________________________________
{
___________________________________________________________________
return new StoneFlooring();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override protected function doCreateBreakableBrick() : DisplayObject
___________________________________________________________________
{
___________________________________________________________________
return new WhiteStone();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override protected function doCreateMoneyBox() : DisplayObject
___________________________________________________________________
{
___________________________________________________________________
return new MoneyBox();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override protected function doCreateCloud() : DisplayObject
___________________________________________________________________
{
___________________________________________________________________
return new AlphaClouds();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override protected function doCreateHill() : DisplayObject
___________________________________________________________________
{
___________________________________________________________________
return new HillSide();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override protected function doCreateBush() : DisplayObject
___________________________________________________________________
{
___________________________________________________________________
return new Bush();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override protected function doCreateCastle() : DisplayObject
___________________________________________________________________
{
___________________________________________________________________
return new Castle();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override protected function doCreatePipe() : DisplayObject
___________________________________________________________________
{
___________________________________________________________________
return new IndustrialPlumbing();
___________________________________________________________________
}
___________________________________________________________________
}
__________________________________________________________________

Listing 9-10. AbstractMarioLevelDirector.as

public class AbstractMarioLevelDirector
{
protected const _width : int = 400;
protected const _height : int = 300;
protected const _bgColor : uint = 0xacccff;
protected var _builder : AbstractMarioEsqueLevelEditor;

public function AbstractMarioLevelDirector( builder :
AbstractMarioEsqueLevelEditor )
{
_builder = builder;
}

public function getLevel() : BitmapData
{
return _builder.getLevel();
}
}

Listing 9-11. QuizLevelDirector.as

public class QuizLevelDirector extends AbstractMarioLevelDirector
___________________________________________________________________
{
___________________________________________________________________
private var rect : Rectangle = new Rectangle( 0 , 0 , 0 , 0 )
___________________________________________________________________

___________________________________________________________________
public function QuizLevelDirector( builder : AbstractMarioEsqueLevelEditor )
___________________________________________________________________
{
___________________________________________________________________
super( builder );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override public function getLevel() : BitmapData
___________________________________________________________________
{
___________________________________________________________________
_builder.width = _width;
___________________________________________________________________
_builder.height = _height;
___________________________________________________________________
_builder.backgroundColor = _bgColor;
___________________________________________________________________
_builder.createMap();
___________________________________________________________________
buildScenicTerrain();
___________________________________________________________________
buildScenicClouds();
___________________________________________________________________
buildScenicBricks();
___________________________________________________________________
buildFloor();
___________________________________________________________________
buildPipes();
___________________________________________________________________
buildMoneyBox();
___________________________________________________________________

___________________________________________________________________
return _builder.getLevel();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
private function buildMoneyBox() : void
___________________________________________________________________
{
___________________________________________________________________
assignRect( 210 , 40 );
___________________________________________________________________
_builder.createMoneyBox( rect );
___________________________________________________________________
assignRect( 80 , 130 );
___________________________________________________________________
_builder.createMoneyBox( rect );
___________________________________________________________________
assignRect( 180 , 130 );
___________________________________________________________________
_builder.createMoneyBox( rect );
___________________________________________________________________
assignRect( 230 , 130 );
___________________________________________________________________
_builder.createMoneyBox( rect );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
private function buildScenicBricks() : void
___________________________________________________________________
{
___________________________________________________________________
assignRect( 155 , 130 , 120 , 23 );
___________________________________________________________________
_builder.createBreakableBrick( rect );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
private function buildPipes() : void
___________________________________________________________________
{
___________________________________________________________________
assignRect( 330 , _height - 15 * 2 - 65 );
___________________________________________________________________
_builder.createPipe( rect );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
private function buildFloor() : void
___________________________________________________________________
{
___________________________________________________________________
assignRect( 0 , _height - 56 , _width , _height - 56 );
___________________________________________________________________
_builder.createSolidBrick( rect );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
private function buildScenicTerrain() : void
___________________________________________________________________
{
___________________________________________________________________
assignRect( 0 , 90 , _width , _height - 56 );
___________________________________________________________________
_builder.createHill( rect );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
private function buildScenicClouds() : void
___________________________________________________________________
{
___________________________________________________________________
assignRect( 0 , 0 , _width , 1 );
___________________________________________________________________
_builder.createCloud( rect );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
private function assignRect( x : int=0, y :
int=0, w : int=0, h : int=0 ) : void
___________________________________________________________________
{
___________________________________________________________________
rect.x = x;
___________________________________________________________________
rect.y = y;
___________________________________________________________________
rect.width = w;
___________________________________________________________________
rect.height = h;
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________

10.Explain why it’s unwise to use a Simple Singleton in an application.

Using a Simple Singleton in AS3 is a bad idea because it doesn’t give you the ability to extend the static instance. Additionally, the Simple Singleton tightly couples code with a static reference, which makes it difficult, or slower, to reuse code in the future.

11.The following code is from an unrevealed class.

Listing 9-12. UnRevealed class

...cont
public function makeFastFoodSandwich( menu_number : int ) : ValueMeal
{
switch(menu_number)
{
case 1:
return new DoubleStack();
break;
case 2 :
return new ChickenSandwich();
break;
case 3:
return new ChickenNuggets();
break;
case 4:
return new Frosty();
break;
}
}
...cont

The code in Listing 9-12 is a factory method. True

12.Twitter is the epitome of which design pattern? The Observer pattern

13.Having parallel hierarchies means you use fewer classes than when using orthogonal hierarchies. True

Quite the contrary. Any time you have parallel hierarchies, you multiply your system by the number of parallel hierarchies.

14.These three patterns can optionally intercept a request before passing it on.

Decorator pattern

Chain of Responsibility pattern

Adapter pattern

15.Show a loose composite that stops all MovieClips in the DisplayList.

//traverse(this.stage)
___________________________________________________________________
public function traverse( mc : DisplayObjectContainer ) : void
___________________________________________________________________
{
___________________________________________________________________
if (mc is MovieClip)
___________________________________________________________________
{
___________________________________________________________________
MovieClip( mc ).stop();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
if (mc.numChildren > 0)
___________________________________________________________________
{
___________________________________________________________________
for ( var i : int = 0; i < mc.numChildren; i++ )
___________________________________________________________________
{
___________________________________________________________________
var innards : DisplayObject = mc.getChildAt( i );
___________________________________________________________________

___________________________________________________________________
if ( innards is MovieClip)
___________________________________________________________________
{
___________________________________________________________________
traverse( MovieClip( innards ) );
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________

16.Re-create the display list from AS3 as a composite.

Listing 9-13. IComponent.as (DisplayObject) interface

public interface IComponent
___________________________________________________________________
{
___________________________________________________________________
function get parentComposite() : Component;
___________________________________________________________________
function set parentComposite( parentComposite : Component ) : void;
___________________________________________________________________
}
___________________________________________________________________

Listing 9-14. IComposite.as (DisplayObjectContainer) interface

public interface IComposite
___________________________________________________________________
{
___________________________________________________________________
function addChild( child : DisplayObject ) : DisplayObject;
___________________________________________________________________
function addChildAt( child : DisplayObject , index : int ) : DisplayObject;
___________________________________________________________________
function getChildAt( index : int ) : DisplayObject;
___________________________________________________________________
function getChildByName( name : String ) : DisplayObject;
___________________________________________________________________
function getChildIndex( child : DisplayObject ) : int;
___________________________________________________________________
function removeChild( child : DisplayObject ) : DisplayObject;
___________________________________________________________________
function removeChildAt( index : int ) : DisplayObject;
___________________________________________________________________
function setChildIndex( child : DisplayObject , index : int ) : void;
___________________________________________________________________
function swapChildren( child1 : DisplayObject , child2 : DisplayObject ) : void;
___________________________________________________________________
function swapChildrenAt( index1 : int , index2 : int ) : void;
___________________________________________________________________
}
___________________________________________________________________

Listing 9-15. Leaf.as (DisplayObject)

public class Leaf implements IComponent
{
}

17.What are the two most significant differences between the State pattern and the Strategy pattern?

1. The Strategy pattern requires the client to change behaviors, whereas the State pattern conceals the behaviors from the client for uniformity. (The state changes itself; the strategy is changed by the client).

2. The change in behaviors in the Strategy pattern reflects the needs of the client, whereas the change in behaviors in the State pattern reflects the change in the context’s state.

Listing 9-16. Loader interface

Listing 9-17. AbstractLoadersContext.as

public class AbstractLoadersContext extends Sprite implements ILoader
___________________________________________________________________
{
___________________________________________________________________
private var _ldr : Loader;
___________________________________________________________________
protected var _stateLoader : ALoaderStateObject;
___________________________________________________________________

___________________________________________________________________
public function AbstractLoadersContext()
___________________________________________________________________
{
___________________________________________________________________
addChild( _ldr = new Loader() );
___________________________________________________________________
_stateLoader = createState( this );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
public function changeState( state : ALoaderStateObject ) : void
___________________________________________________________________
{
___________________________________________________________________
_stateLoader.dispose();
___________________________________________________________________
_stateLoader = state;
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
public function close() : void
___________________________________________________________________
{
___________________________________________________________________
_stateLoader.close();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
public function get content() : DisplayObject
___________________________________________________________________
{
___________________________________________________________________
return _stateLoader.content;
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
public function get contentLoaderInfo() : LoaderInfo
___________________________________________________________________
{
___________________________________________________________________
return _stateLoader.contentLoaderInfo;
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
public function load( request:URLRequest, context:LoaderContext = null ) : void
___________________________________________________________________
{
___________________________________________________________________
_stateLoader.load( request , context );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
public function loadBytes( bytes:ByteArray, context:LoaderContext = null ) : void
___________________________________________________________________
{
___________________________________________________________________
_stateLoader.loadBytes( bytes , context );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
public function get ldr() : Loader
___________________________________________________________________
{
___________________________________________________________________
return _ldr;
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
public function dispose() : void
___________________________________________________________________
{
___________________________________________________________________
_stateLoader.dispose();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
protected function createState( abstractLoadersContext :
AbstractLoadersContext) : ALoaderStateObject
___________________________________________________________________
{
___________________________________________________________________
throw new IllegalOperationError( 'createState must be overridden' )
___________________________________________________________________
return null;
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________

Listing 9-18. LoadersContext.as

public class LoadersContext extends AbstractLoadersContext
___________________________________________________________________
{
___________________________________________________________________
public function LoadersContext()
___________________________________________________________________
{
___________________________________________________________________
super();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override protected function createState( abstractLoadersContext :
AbstractLoadersContext ) : ALoaderStateObject
___________________________________________________________________
{
___________________________________________________________________
return EmptyLoaderStateObject( abstractLoadersContext );
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________

Explanation: LoadersContext uses a factory method, whereas the StateObjects don’t, because LoadersContext declares the initial StateObject. This is subject to change more than the StateObjects because the individual states typically have a particular successor.

Listing 9-19. ALoaderStateObject.as extends Object

public class ALoaderStateObject extends Object
___________________________________________________________________
{
___________________________________________________________________
protected var _ldrContext : LoadersContext;
___________________________________________________________________
protected var _ldr : Loader;
___________________________________________________________________

___________________________________________________________________
public function ALoaderStateObject( context : LoadersContext )
___________________________________________________________________
{
___________________________________________________________________
_ldrContext = context;
___________________________________________________________________
_ldr = context.ldr;
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
public function close() : void
___________________________________________________________________
{
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
public function get content() : DisplayObject
___________________________________________________________________
{
___________________________________________________________________
return null;
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
public function get contentLoaderInfo() : LoaderInfo
___________________________________________________________________
{
___________________________________________________________________
return null;
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
public function load( request:URLRequest , context:LoaderContext = null ) : void
___________________________________________________________________
{
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
public function loadBytes( bytes:ByteArray, context:LoaderContext = null ) : void
___________________________________________________________________
{
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
public function unload() : void
___________________________________________________________________
{
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
public function unloadAndStop( gc : Boolean = true ) : void
___________________________________________________________________
{
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
public function get ldr() : Loader
___________________________________________________________________
{
___________________________________________________________________
return _ldr;
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
public function set ldr( ldr : Loader ) : void
___________________________________________________________________
{
___________________________________________________________________
_ldr = ldr;
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
public function dispose() : void
___________________________________________________________________
{
___________________________________________________________________
throw new IllegalOperationError( 'dispose must be overridden' );
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________

Listing 9-20. EmptyLoaderStateObject.as extends ALoaderStateObject

public class EmptyLoaderStateObject extends ALoaderStateObject
___________________________________________________________________
{
___________________________________________________________________
public function EmptyLoaderStateObject( context : LoadersContext )
___________________________________________________________________
{
___________________________________________________________________
super( context );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override public function get contentLoaderInfo() : LoaderInfo
___________________________________________________________________
{
___________________________________________________________________
return _ldr.loaderInfo;
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override public function load( request:URLRequest , context:LoaderContext = null ) : void
___________________________________________________________________
{
___________________________________________________________________
_ldr.load( request , context );
___________________________________________________________________
_ldrContext.changeState( new OpeningConnectionStateObject( _ldrContext ) );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override public function loadBytes( bytes:ByteArray , context:LoaderContext = null ) : void
___________________________________________________________________
{
___________________________________________________________________
_ldr.loadBytes( bytes , context );
___________________________________________________________________
_ldrContext.changeState( new OpeningConnectionStateObject( _ldrContext ) );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override public function dispose() : void
___________________________________________________________________
{
___________________________________________________________________
_ldr = null;
___________________________________________________________________
_ldrContext = null;
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________

Listing 9-21. OpeningConnectionStateObject.as extends ALoaderStateObject

public class OpeningConnectionStateObject extends ALoaderStateObject
___________________________________________________________________
{
___________________________________________________________________
public function OpeningConnectionStateObject( context : LoadersContext )
___________________________________________________________________
{
___________________________________________________________________
super( context );
___________________________________________________________________
_ldr.contentLoaderInfo.addEventListener( Event.OPEN , onConnectionOpen );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
private function onConnectionOpen( event : Event ) : void
___________________________________________________________________
{
___________________________________________________________________
_ldrContext.changeState( new LoadingStateObject( _ldrContext ) );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override public function get contentLoaderInfo() : LoaderInfo
___________________________________________________________________
{
___________________________________________________________________
return ldr.loaderInfo
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override public function dispose() : void
___________________________________________________________________
{
___________________________________________________________________
_ldr.contentLoaderInfo.removeEventListener( Event.OPEN , onConnectionOpen );
___________________________________________________________________
_ldr = null;
___________________________________________________________________
_ldrContext = null;
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________

Listing 9-22. LoadingStateObject.as extends ALoaderStateObject

public class LoadingStateObject extends ALoaderStateObject
___________________________________________________________________
{
___________________________________________________________________
public function LoadingStateObject( context : LoadersContext )
___________________________________________________________________
{
___________________________________________________________________
super( context );
___________________________________________________________________
_ldr.contentLoaderInfo.addEventListener( Event.COMPLETE , onComplete );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
private function onComplete( event : Event ) : void
___________________________________________________________________
{
___________________________________________________________________
_ldrContext.changeState( new LoadedStateObject( _ldrContext ) );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override public function close() : void
___________________________________________________________________
{
___________________________________________________________________
_ldr.close();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override public function get contentLoaderInfo() : LoaderInfo
___________________________________________________________________
{
___________________________________________________________________
return ldr.loaderInfo;
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override public function load( request:URLRequest, context:LoaderContext ) : void
___________________________________________________________________
{
___________________________________________________________________
close();
___________________________________________________________________

___________________________________________________________________
_ldr.load( request , context );
___________________________________________________________________
_ldrContext.changeState( new OpeningConnectionStateObject( _ldrContext ) );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override public function loadBytes( bytes:ByteArray,context:LoaderContext ) : void
___________________________________________________________________
{
___________________________________________________________________
close();
___________________________________________________________________
_ldr.loadBytes( bytes , context );
___________________________________________________________________
_ldrContext.changeState( new OpeningConnectionStateObject( _ldrContext ) );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override public function dispose() : void
___________________________________________________________________
{
___________________________________________________________________
_ldr.contentLoaderInfo.removeEventListener( Event.COMPLETE , onComplete );
___________________________________________________________________
_ldr = null;
___________________________________________________________________
_ldrContext = null;
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________

Listing 9-23. LoadedStateObject.as extends ALoaderStateObject

public class LoadedStateObject extends ALoaderStateObject
___________________________________________________________________
{
___________________________________________________________________
public function LoadedStateObject( context : LoadersContext )
___________________________________________________________________
{
___________________________________________________________________
super( context );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override public function close() : void
___________________________________________________________________
{
___________________________________________________________________
_ldr.unloadAndStop();
___________________________________________________________________
_ldr.unload();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override public function get contentLoaderInfo() : LoaderInfo
___________________________________________________________________
{
___________________________________________________________________
return _ldr.loaderInfo;
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override public function load( request:URLRequest , context:LoaderContext = null ) : void
___________________________________________________________________
{
___________________________________________________________________
close();
___________________________________________________________________
_ldr.load( request , context );
___________________________________________________________________
_ldrContext.changeState( new OpeningConnectionStateObject( _ldrContext ) );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override public function loadBytes( bytes:ByteArray , context:LoaderContext = null) : void
___________________________________________________________________
{
___________________________________________________________________
close();
___________________________________________________________________
_ldr.loadBytes( bytes , context );
___________________________________________________________________
_ldrContext.changeState( new OpeningConnectionStateObject( _ldrContext ) );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override public function dispose() : void
___________________________________________________________________
{
___________________________________________________________________
_ldr = null;
___________________________________________________________________
_ldrContext = null;
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________

19.Write an AbstractShape class and its subclasses, Square and Circle, so they can be drawn and cleared. Additionally, construct an AbstractCommand class that can execute and unexecute code. There are two possible solutions; write both.

Listing 9-24. IGraphics.as interface

public interface IGraphics
___________________________________________________________________
{
___________________________________________________________________
function draw() : void;
___________________________________________________________________
function clear() : void;
___________________________________________________________________
function get parent() : DisplayObjectContainer;
___________________________________________________________________
}
___________________________________________________________________

Listing 9-25. AbstractShape.as constants WIDE and TALL are both 20 pixels. FILL_COLOR is yellow.

public class AbstractShape extends Shape implements IGraphics
___________________________________________________________________
{
___________________________________________________________________
protected const WIDE : int = 20;
___________________________________________________________________
protected const TALL : int = 20;
___________________________________________________________________
private const FILL_COLOR : uint = 0xfff000;
___________________________________________________________________

___________________________________________________________________
final public function draw() : void
___________________________________________________________________
{
___________________________________________________________________
addColor();
___________________________________________________________________
doDraw();
___________________________________________________________________
endFill();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
final public function clear() : void
___________________________________________________________________
{
___________________________________________________________________
this.graphics.clear();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
protected function doDraw() : void
___________________________________________________________________
{
___________________________________________________________________
throw new IllegalOperationError( 'doDraw must be overridden' );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
private function addColor() : void
___________________________________________________________________
{
___________________________________________________________________
this.graphics.beginFill( FILL_COLOR , 1 );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
private function endFill() : void
___________________________________________________________________
{
___________________________________________________________________
this.graphics.endFill();
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________

Listing 9-26. CircleShape.as

public class CircleShape extends AbstractShape
___________________________________________________________________
{
___________________________________________________________________
override protected function doDraw() : void
___________________________________________________________________
{
___________________________________________________________________
var radius : Number = Math.sqrt( WIDE * WIDE + TALL * TALL );
___________________________________________________________________
this.graphics.drawCircle( 0 , 0 , radius );
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________

Listing 9-27. SquareShape.as

___________________________________________________________________
public class SquareShape extends AbstractShape
___________________________________________________________________
{
___________________________________________________________________

___________________________________________________________________
override protected function doDraw() : void
___________________________________________________________________
{
___________________________________________________________________
this.graphics.drawRect( 0 , 0 , WIDE , TALL );
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________

Listing 9-28. AbstractShapeCommand.as

public class AbstractShapeCommand
___________________________________________________________________
{
___________________________________________________________________
protected var _receiver : IGraphics;
___________________________________________________________________

___________________________________________________________________
public function AbstractShapeCommand( rcvr : IGraphics )
___________________________________________________________________
{
___________________________________________________________________
_receiver = rcvr;
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
final public function execute() : void
___________________________________________________________________
{
___________________________________________________________________
doExecute();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
protected function doExecute() : void
___________________________________________________________________
{
___________________________________________________________________
throw new IllegalOperationError( 'doExecute must be overridden' );
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________

Listing 9-29. ShapeCommandDraw.as

public class ShapeCommandDraw extends AbstractShapeCommand
___________________________________________________________________
{
___________________________________________________________________
override protected function doExecute() : void
___________________________________________________________________
{
___________________________________________________________________
_receiver.draw();
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________

Listing 9-30. ShapeCommandUndo.as

public class ShapeCommandUndo extends AbstractShapeCommand
___________________________________________________________________
{
___________________________________________________________________
override protected function doExecute() : void
___________________________________________________________________
{
___________________________________________________________________
_receiver.clear();
___________________________________________________________________
_receiver.parent.removeChild( DisplayObject( _receiver ) );
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________

Listing 9-31. AbstractShapeUndoCommand.as

public class AbstractShapeUndoCommand extends AbstractShapeCommand
___________________________________________________________________
{
___________________________________________________________________
public function undo() : void
___________________________________________________________________
{
___________________________________________________________________
doUndo();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
protected function doUndo() : void
___________________________________________________________________
{
___________________________________________________________________
throw new IllegalOperationError( 'doUndo must be overridden' );
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________

Listing 9-32. ShapeCommandWithUndo.as

public class ShapeCommandWithUndo extends AbstractShapeUndoCommand
___________________________________________________________________
{
___________________________________________________________________
override protected function doExecute() : void
___________________________________________________________________
{
___________________________________________________________________
_receiver.draw();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
override protected function doUndo() : void
___________________________________________________________________
{
___________________________________________________________________
_receiver.clear();
___________________________________________________________________
_receiver.parent.removeChild( DisplayObject( _receiver ) );
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________

20.The Execute method accompanies which design pattern?

The Command pattern

21.Explain the advantage of the Abstract Factory pattern over the Factory Method pattern

Unlike a factory method, an abstract factory is an object that manufactures products. This allows the abstract factory to be parameterized among other objects to which the manufacturing request can be delegated.

22.In ActionScript 3.0, what are the three design patterns used in the EventSystem to carry out events of DisplayObjects?

Composite pattern

Chain of Responsibility pattern

Observer pattern

23.Three objects make up an image loader in an application: a loader, an image mask, and a description box. Using these three objects, the sequence must occur in the following order:

a. An image loads.

b. The mask transitions to reveal the image.

c. Text appears, giving a description.

Demonstrate how the Chain of Responsibility pattern can properly compliment the output of the following client code in Listing 9-33.

Listing 9-33. DocumentClass using the Chain of Responsibility pattern to accomplish its sequence

Listing 9-34. IHandler interface

public interface IHandler
___________________________________________________________________
{
___________________________________________________________________
function addHandler( successor : IHandler ) : void;
___________________________________________________________________

___________________________________________________________________
function forward() : void;
___________________________________________________________________
}
___________________________________________________________________

Listing 9-35. AbstractView

public class AbstractView extends Sprite implements IHandler
___________________________________________________________________
{
___________________________________________________________________
protected var _handler : IHandler;
___________________________________________________________________

___________________________________________________________________
public function AbstractView()
___________________________________________________________________
{
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
public function addHandler( successor : IHandler ) : void
___________________________________________________________________
{
___________________________________________________________________
_handler = successor;
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
final public function forward() : void
___________________________________________________________________
{
___________________________________________________________________
doForward();
___________________________________________________________________
_handler.forward();
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
protected function doForward() : void
___________________________________________________________________
{
___________________________________________________________________
trace( this + ' target hit' );
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________

Listing 9-36. ImageView.as loads the following image: www.spilled-milk.com/000.jpg.

public class ImageView extends AbstractView
___________________________________________________________________
{
___________________________________________________________________
protected var ldr : Loader
___________________________________________________________________

___________________________________________________________________
public function ImageView()
___________________________________________________________________
{
___________________________________________________________________
super();
___________________________________________________________________
ldr = new Loader();
___________________________________________________________________
ldr.contentLoaderInfo.addEventListener( Event.COMPLETE , onImageLoad ) ;
___________________________________________________________________
ldr.load( new URLRequest( "http://www.spilled-milk.com/000.jpg" ) );
___________________________________________________________________
addChild( ldr );
___________________________________________________________________
}
___________________________________________________________________

___________________________________________________________________
public function onImageLoad( event : Event ) : void
___________________________________________________________________
{
___________________________________________________________________
forward();
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________

Listing 9-37. MaskView

public class MaskView extends AbstractView
___________________________________________________________________
{
___________________________________________________________________
public function MaskView()
___________________________________________________________________
{
___________________________________________________________________
super();
___________________________________________________________________
}
___________________________________________________________________
}
___________________________________________________________________

Listing 9-38. TextFieldView

public class TextFieldView extends AbstractView
___________________________________________________________________
{
___________________________________________________________________
public function TextFieldView()
___________________________________________________________________
{
___________________________________________________________________
super();
___________________________________________________________________
}
}
___________________________________________________________________

24.What pattern decouples multiple subsystems from client messaging by funneling those implementations into a simpler interface? The façade pattern

25.Choose the appropriate associations: