12 | Chapter 1: Object-Oriented Programming, Design Patterns, and ActionScript 3.0
skills that would provide the concrete details for each position. For example, one
programmer may have PHP middleware skills and/or MySQL database skills, while
another may be experienced in using ASP.NET, C# and MS SQL. The abstraction is
in the job description and the details are provided by the applicants’ unique sets of
skills and experience.
InObject-Oriented Design with Applications(Benjamin/Cummings), Grady Booch,
one of the design pattern pioneers, provides the following definition of an abstrac-
tion that is both clear and succinct:
An abstraction denotes the essential characteristics of an object that distinguish it from
all other kinds of object and thus provide crisply defined conceptual boundaries, rela-
tive to the perspective of the viewer.Booch’s definition pretty well describes the two job descriptions. The descriptions
provide the essential characteristics of the position and they distinguish one from the
other.
Abstractions in ActionScript 3.0
Turning now to abstractions in ActionScript programming, we’ll take a simple video
player for an example. This player will be made of certain elements that we need; so
we start by listing them as abstractions:
- A Net connection
- A video screen
- A stream
- An FLV file to play
If we put these together just right, we’ll be able to play a video. However, instead of
starting with an abstraction, we want to start with something concrete that works for
us right away. Enter the code in Example 1-2 saving the file using the name in the
caption:
Throughout the book, with a few exceptions, caption names repre-
sent the name used for the file.Example 1-2. PlayVideo.as
package
{
import flash.net.NetConnection;
import flash.net.NetStream;
import flash.media.Video;
import flash.display.Sprite;
public class PlayVideo extends Sprite