ActionScript 3.0 Design Patterns

ARE Design Patterns portable from one language to another? Of course they are. I’ve read some accounts that claim otherwise, but I’ve not found any design pattern that could not be used in any computer language that I’ve tried. (Maybe I’m just conversant in languages where design patterns do work, but I don’t think so.) Anyway, Chandima and I have been discussing doing a set of PHP design patterns, and I wanted one for a contact form I had done using PHP.

For this blog, though, I thought I’d use a translation from one of the design patterns we have on this blog so that you can more easily see the similarities and differences between ActionScript 3.0 and PHP in implementing the same design pattern.

Chain of Responsibility

As you may recall from our Chain Of Responsibility (CoR) post, the design pattern is used when you want to have a system that takes care of requests when you have different outcomes. In our original example, we added a helper class called Request, but otherwise we stuck with the basics of the CoR structure. Figure 1 shows the class diagram of the CoR we used in our initial post.

Figure 1: Chain of Responsibility Class Diagram

In this particular design pattern the Client class is a full-fledged participant in the pattern. Because Client classes are request objects themselves, it may seem odd to have a Request class. Just think of the Request class as a helper class that encapsulates requests for the Client.
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Note: This is one of those posts that begs for reader comments. PHP is a much-loved language of mine, but I just don’t do the kind of applications that require PHP often. As a result, it stays on the shelf until I need it. So, while very familiar with PHP, I do not claim a high level expertise in it. However, judging from the online PHP discussions and PHP publications, lots of developers are well versed in the language. So, for you PHP’ers out there, your comments are welcomed. (Likewise if you’re not familiar with PHP, feel free to comment as well.)

PHP, My Old Friend

PHP has always been a developers programming language. From its inception, you could write PHP using Notepad or TextEdit and not have to worry about some cranky API or IDE. Alternatively, there are plenty of development applications for creating PHP, such as Dreamweaver. Further, you could write email apps as easy as a ‘Hello World’ example. Not only is PHP open source, it is constantly updated and improved by developers working on it because it is important to them. You can plunk it down on top of an Apache server (also open source) and use MySQL (also open source—but maybe not for long) for a database. It runs on Linux, Windows and on Mac OS (it comes standard with Macs as does an Apache server). Further, PHP 5 has real abstract classes! What’s not to like?
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