hubuse - Using the Hub library
The Hub module represents functions and classes which are implemented in descendant packages. Hub dynamically loads modules according to the parameters it is used with.
Don't use the underlying modules directly:
use Hub::Base::FileSystem; # Wrong use Hub; # Correct
my $parser = Hub::Parse::FileParser->new('my.template'); # Wrong
my $parser = Hub::mkinst('FileParser', 'my.template'); # Correct
Without getting into gory detail, this non-standard approach is in place for three reasons:
1) Allow the library to be refactored (maintained) without impacting existing
code.
2) We don't want to short-circut Perl's built-in require functionality which
would be necessary, were we to support direct underlying module usage.
3) We only want to load underlying modules when they are needed. We want to
group related modules in the same subdirectory. The subdirectory name
will then be used as the import tag which loads its modules.
By default, Hub tries to be as efficient as possible, only loading packages which are necessary.
Subdirectories are used to group exported modules. Underneath the root (Hub) directory, are sub-directories which represent the export tag of which the underlying modules should be represented.
Hub/:
|-Base/:
|-Util/:
`-Webapp/:
Descendant packages maintain their exported symbols in their EXPORT_OK array. The Hub module proxies these exported symbols, thus requiring all descendant- exported symbols to be unique.
Classes are created with the Hub::mkinst using their short-name. Thus requiring them to be unique (to other classes):
1. Hub::Custom::Class.pm # defines function 'new' 2. Hub::Another::Class.pm # doesn't define 'new' 3. Hub::Yetagain::Class.pm # also defines 'new'
#1 and #3 will clash because they are both classes, but either can be used with #2 simultaneously.
Ryan Gies (ryangies@livesite.net)
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06/09/2007