58 | Chapter 1: Object-Oriented Programming, Design Patterns, and ActionScript 3.0
and ActionScript 3.0. However, the plan illustrates a basic truth about software in
general and web development in particular. You’re going to spend more time on
maintenance and changing a site than you are building it in the first place. As a
result, you need to plan for maintenance and extensibility, and not just to get things
working right in the first place.
Had the web site that had been planned for change been done with design patterns,
not only would it be able to adapt to change, we wouldn’t have to scrap the current
design and start all over from scratch to extend the site. That is, only part of the
planning process should address change of a static category. You also need to plan
for extending the site to incorporate more than what you originally planned to
change. That is, you may need to add new materials to change.
Planning Only for Maintenance
While the web site described asbuilt for changehas persisted, it has not evolved. The
site has been easy to maintain because its main function loads an image, a text file,
and menu items for a given product. By either changing the label on an existing but-
ton or adding a button, changing and adding products is pretty simple as well. So it
has a little extensibility in the sense that its not fixed to a single product.
However, the site really isn’t set up for robust extensibility. For instance, adding a
blog to the site or changing the way that the menus work would take the same
amount of re-structuring as it would to start from scratch. So, while changing prod-
ucts in the site is simple, changing the site is not. Structurally, the site looks some-
thing like Figure 1-9—The Big Function.
It doesn’t matter whether the big function is directly instantiated, gained through
inheritance, or a delegate of composition. It has no flexibility other than the parame-
ter to tell it what to place on the stage. If its algorithm is changed, it could wreck
havoc on its use. You can view it as tough and inflexible because it gets one job done
in one way. Alternatively, the big function can be seen as dainty and fragile because
of its dependency on a single routine, and because it is subject to freeze up when
Figure 1-9. The Big Function
function BigFunction (product)
{
load image in SWF
load text from text file
load menu items into array
load array into Combo box
}The Big Function