42 | Chapter 1: Object-Oriented Programming, Design Patterns, and ActionScript 3.0
In addition to messages in the Output window, you should see something like
Figure 1-6 on the stage.
In addition to the visible graphics, you should also hear the sound played by the
MP3 file. (This multimedia experience has been brought to you by polymorphism
and the letterP.)
Principles of Design Pattern Development
The founding principles of design patterns are laid down in the Gang of Four’s (GoF)
canon,Design Patterns: Elements of Reusable Object-Oriented Software. The two
essential principles are:
- Program to an interface, not an implementation
- Favor object composition over class inheritance
If you skipped the section on the four basic OOP principles because you already
know them, the first principle of Design Pattern OOP was introduced, but only
briefly. Not to worry, we’ll go over it in detail.
Before going further, we need to clarify some basic terms. While these terms are
fairly simple, they can trip you up if you don’t understand how they’re used in
Figure 1-6. Graphic file and video appear on the stage