Archive for the 'Builder' Category

ActionScript 3.0 Builder Design Pattern Part II: Multiple Builds

Published on December 1, 2009 in Builder. by William B. Sanders 1 Comment

As a concrete follow-up to Part I of this two-part post, I thought that once I decided on which graphics, text and video to use the development would go pretty quickly. It took a lot longer than I thought, but now that the concrete example is ready it’s pretty easy to see how to put a practical Builder together and re-use and extend it. Because this second part builds on the first part, if you’re only vaguely familiar with the Builder Design Pattern, you might want to review Part I.

What to Build?

In ActionScript 3.0 Builder Design Pattern Part I, we set up a vacation-building site using trace statements to display different characteristics. To make these characteristics come alive and work in some practical matter, the goal is to create a builder that does the following:

  • Load an external graphic
  • Play a video that can be displayed in any format used by Flash Media Server or Progressive Download
  • Display a different background for each vacation destination. The background is made of an external .swf file
  • Present text write-up using external text source

In looking at those four actions, you might be thinking, that’s not exactly rocket science. You’d be right. However, when you start adding more and more vacation destinations, keeping track of everything can dampen one’s resolution. With the Builder, though, I found it very easy to add, change, and delete. In fact, I encourage you to add your own favorite vacation place and add it using the builder described in this post.

The Design

In Part I, I talked about different variations in the Builder’s design. The one we’re using closely follows the first as far as the Product class is concerned. All of the concrete builder classes use the same Product class. The Product class assembles the different parts under construction. However, in order to keep the Product class manageable, I added several Helper classes to take care of the details for the different parts that need to be built for the final product. Figure 1 shows the file pattern for the design:

<em><strong>Figure 1: </strong> File Class Diagram of Builder Design Pattern</em>

Figure 1: File Class Diagram of Builder Design Pattern

As you can see, several classes use the Product class, and it uses all of the helper classes. Even the Client holds a reference to the Product class. As far as design is concerned, though, this one is identical to the one we used in Part I with the added helper classes.
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ActionScript 3.0 Builder Design Pattern Part I: Controlling Creation

Published on March 17, 2009 in ActionScript, Builder and Design Patterns. by William B. Sanders 6 Comments

Changing How a Composite Object Gets Created

In both our book and on this blog, Chandima and I have tried to clarify and simplify ActionScript 3.0 Design Patterns and yet keep them accurate and, whenever possible, practical. After reviewing many, many Builder examples, I was surprised to find pieces missing in several instances, and while the examples may have combined elements (such as the Client and Director); others simply left out crucial components. (Who could forget bad, bad Leroy Brown who looked like a jigsaw puzzle with a couple of pieces gone?)

Given this state of affairs, it occurred to me that this pattern might be tricky; however, after working up an example, it turns out to be relatively simple and useful. Nevertheless, it’s not quite as simple as some, such as the Strategy or Factory Method, and so the discussion of the Builder is in two parts. This first part provides a clear overview so that you can easily see how the different components work together and starts a practical project., The second part (in a separate post) removes the abstract trace statements and displays actual content on the stage in a useful way. This will be to see if video, SWF, text, and images can be usefully integrated using the Builder.

Builder Overview

When you first look at the Builder class diagram shown in Figure 1, you might think it looks a lot like the Strategy pattern. Well, the class diagrams are similar, but the intent is very different. Also, you’ll find that the little Product class is hugely important.

builder
Figure 1: Builder Class Diagram
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