Algorithm::Dependency:UserrContributed Perl DoAlgorithm::Dependency::Source(3)NAMEAlgorithm::Dependency::Source - Implements a source of heirachy items
DESCRIPTION
The Algorithm::Dependency::Source class provides an abstract parent
class for implementing sources for the heirachy data the algorithm will
use. For an example of an implementation of this, see
Algorithm::Dependency::Source::File, which is bundled with the main
Algorithm::Dependency package.
METHODS
new @arguments
Although you cannot directly use the "new" constructor for
"Algorithm::Dependency::Source", it will work the same in all
subclasses.
The constructor takes zero or more subclass specific arguments to
define the location of the source of the items, and returns a new
object. Alrough it may check that the arguments you passed are valid,
the source will usually NOT actually load the items from the source,
instead defering the loading until you need to use the items.
Returns a new object on success, or "undef" on error.
load
The "load" method is the public method used to actually load the items
from their storage location into the the source object. The method will
automatically called, as needed, in most circumstances. You would
generally only want to use "load" manually if you think there may be
some uncertainty that the source will load correctly, and want to check
it will work.
Returns true if the items are loaded successfully, or "undef" on error.
item $name
The "item" method fetches and returns the item object specified by the
name argument.
Returns an Algorithm::Dependency::Item object on success, or "undef" if
the named item does not exist in the source.
items
The "items" method returns, as a list of objects, all of the items
contained in the source. The item objects will be returned in the same
order as that in the storage location.
Returns a list of Algorithm::Dependency::Item objects on success, or
"undef" on error.
missing_dependencies
By default, we are leniant with missing dependencies if the item is
neved used. For systems where having a missing dependency can be very
bad, the "missing_dependencies" method checks all Items to make sure
their dependencies exist.
If there are any missing dependencies, returns a reference to an array
of their ids. If there are no missing dependencies, returns 0. Returns
"undef" on error.
EXTENDING
"Algorithm::Dependency::Source" itself is a fairly thin module, and it
is intended that you will probably need to extend it to be able to
extract item data from whatever location you have stored them.
This is usually a fairly simple two step process.
Overload the "new" method.
Assuming your subclass takes some form or argument on creation, you
will need to overload the "new" method to accept the arguments,
validate them, and store them in the source object.
Define the method "_load_item_list".
Leaving our parent's "load" method to take care of conflict,
errors, and whatever, the "_load_item_list" method is used to
simply create a list of Algorithm::Dependency::Item objects from
wherever you store the item, and return them as a list.
Having completed these two things, your subclass should be completed.
For an example of the code, have a look at the source for the simple
subclass Algorithm::Dependency::Source::File.
SUPPORT
For general comments, contact the author.
To file a bug against this module, in a way you can keep track of, see
the CPAN bug tracking system.
http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Algorithm-Dependency
<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Algorithm-Dependency>
AUTHOR
Adam Kennedy <adamk@cpan.org>
SEE ALSO
Algorithm::Dependency, Algorithm::Dependency::Source::File
COPYRIGHT
Copyright 2003 - 2009 Adam Kennedy.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
The full text of the license can be found in the LICENSE file included
with this module.
perl v5.14.1 2009-04-14 Algorithm::Dependency::Source(3)
