ActionScript 3.0 Design Patterns

I ran across the Flyweight design pattern when looking for a pattern that could be used to speed up placing objects on the stage in a Flash application using ActionScript 3.0. The Flyweight name implies a somewhat insignificant design pattern, but after working with it for a few months I found it to be both powerful and informative. It is powerful in that it is one pattern that actually speeds up operations, and it’s informative in that key OOP concepts are used and illuminated in it. It’s also one that has taken a while to really put together right—a process I’m still working on. Because this is a work in progress, I’d like to invite any and all developers with an interest in ActionScript 3.0 and design patterns to comment.
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In AS2, declaring a constructor as private in a class prevented it from being instantiated. Unlike AS2, constructor methods cannot be declared as private in ActionScript 3.0. This killed the simple runtime check for abstract class instantation. Sho Kuwamoto, Senior Director of Engineering at Adobe describes the thought process behind the omission of private constructors in AS3.

A more creative approach to implementing abstract classes is necessary in AS3. The issue of preventing instantiation of abstract classes in AS3 has been looked into very throughly by several developers such as Tink and Mims Wright. The solution is quite simple, but how do we make sure that abstract methods have been implemented in subclasses as well? This post describes one solution (Mims has another) to this issue using the concept of type introspection in ActionScript 3.0.
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Our latest book is currently on O’Reilly rough cuts with expected publication in July 2007. This hands-on introduction to design patterns is for experienced Flash developers ready to tackle sophisticated programming techniques with ActionScript 3.0. The book takes you through the process step by step, explaining how design patterns provide a clear road map for structuring code that actually makes OOP languages easier to use. During the course of the book, you will work with many examples. We introduce design patterns with minimalist examples before going on to build full-fledged working applications.