It should come as no surprise that between the Apache distribution and third-party modules, there exist dozens of authentication modules, several directory indexing modules, and a couple of extended server-side include modules. All of these modules contain code that was copied and pasted from each other. In some cases all but a minuscule portion of the module consists of duplicated code.
Code duplication is not bad in and of itself, but it is wasteful of memory resources and, more important, of developers' time. It would be much better if code could be reused rather than duplicated, by using a form of object-oriented subclassing. For the C-language API there's not much hope of this. Vanilla C doesn't provide object-oriented features, while C++ would require both the Apache core and every extension module to adopt the same class hierarchy—and it's a little late in the game for this to happen.
Fortunately, the Perl language does support a simple object-oriented model that doesn't require that everyone buy into the same class hierarchy. This section describes how these object-oriented features can be used by Perl API modules to reuse code instead of duplicating it.
We've already looked at piecing together documents in various ways. Here we will explore an implementation using method handlers. There are two classes involved with this example: My::PageBase and My::Page.
Example 4.26 shows the My::PageBase class, which provides the base functionality for the ...