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Using Flash MX ActionScript
Object Oriented Techniques
What is an Object?
An object is an abstract representation of a thing or concept that programmers
can use as containers for both data and code. With ActionScript we can set
an object’s properties by specifying the object, and then naming the
property, such as this example:
myMusic.style = “Jazz”;
According to Hall, the basic concepts of behind OOP (Object Oriented Programming)
are objects, properties, methods, and classes (p. 34, 2002). If you want to
learn more about Branden Hall's ideas you can go to his companion website
for his OOP book at http://www.wheelmaker.org/.
Why use OOP in Flash?
Even when you are not using OOP with Flash movies you will still need to
plan how your movies are going to be created. Each scene needs to be written
out
so you know how you are going to program or create the movie. Hall writes about
the process of building Macromedia Flash applications is similar to building
a house, and offers the following advice (at http://www.macromedia.com/devnet/mx/flash/extreme/extreme005.html,
2003):
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Drawing the blueprints includes making a plan using the Model-View-Controller
(MVC) pattern. This entails the model, which handles your application’s
data; the view, which handles the visual interface; and the controller, which
handles the user input.
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Pouring the foundation which consists of the application data and accessor
methods to retrieve and modify that data.
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Framing, wiring, and plumbing consists of two pieces: the view (what the user
sees and interacts with), and the controller (which handles user input – for
example, validation).
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Wallpaper and paint consists of making the application pretty, such as, adding
backgrounds and colors.
OOP allows programmers to manage their project in smaller pieces, which allows
the project to flow smoother.
How do you apply OOP in Flash?
By looking at the Flash environment as many objects of which you can use to
build other objects you can use them to create the applications how you desire.
Bhangal writes that the open-ended approach is not used much in classic OOP,
but the freeform ‘create objects and then build other stuff on top of
them in an open process’ is what Flash is all about (p. 391, 2002).
In Flash all objects are built upon what is called the Object object, and
this is important because it is the base of all objects in Flash. Bhangal
discusses
that there are only two important things: the object > .property/method
structure and scope (p.400, 2002):
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All objects are fundamentally data structures, consisting of properties and
methods. This structure is inherited from a base object called Object.
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Some properties are expressed as data and some are expressed as visual attributes,
but neither are special cases, because the code that controls a property is
fundamentally the same, irrespective of what the effect of changing the property
will be.
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All objects conform to scope. There are two way of assigning scope, one of
which is visual (e.g. attaching MovieClips, Buttons, and TextFields to a keyframe),
and the other is programmatical (defining an object within a script that is
also attached to a keyframe). Neither is a special case, and both are actually
different ways of doing the same thing.
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One object is unique because it has no scope and this is called _global. Rather
than see this as a new object, it is better to see it as a special case of
position (or scope= =null or scope = = everywhere, depending on how you prefer
to see it). It is timeline-independent and therefore not a timeline itself,
but a position. Objects that are global are not special cases, but simply normal
objects in a special scope-less place.
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