view release on metacpan or  search on metacpan

lib/Algorithm/Dependency/Source.pm  view on Meta::CPAN

=head1 METHODS

=head2 new @arguments

Although you cannot directly use the C<new> constructor for
C<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. Although it
may check that the arguments you passed are valid, the source will usually
NOT actually load the items from the source, instead deferring the loading
until you need to use the items.

Returns a new object on success, or C<undef> on error.

=head2 load

The C<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 C<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 C<undef> on error.

=head2 item $name

The C<item> method fetches and returns the item object specified by the
name argument.

Returns an L<Algorithm::Dependency::Item> object on success, or C<undef> if
the named item does not exist in the source.

=head2 items

The C<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 L<Algorithm::Dependency::Item> objects on success, or
C<undef> on error.

=head2 missing_dependencies

By default, we are lenient with missing dependencies if the item is never 
used. For systems where having a missing dependency can be very bad, the 
C<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 
C<undef> on error.

=head1 EXTENDING

C<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.

=over 4

=item Overload the C<new> method.

Assuming your subclass takes some form or argument on creation, you will
need to overload the C<new> method to accept the arguments, validate them,
and store them in the source object.

=item Define the method C<_load_item_list>.

Leaving our parent's C<load> method to take care of conflict, errors, and
whatever, the C<_load_item_list> method is used to simply create a list of
L<Algorithm::Dependency::Item> objects from wherever you store the item,
and return them as a list.

=back

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
L<Algorithm::Dependency::Source::File>.

=head1 SEE ALSO

L<Algorithm::Dependency>, L<Algorithm::Dependency::Source::File>

=head1 SUPPORT

Bugs may be submitted through L<the RT bug tracker|https://rt.cpan.org/Public/Dist/Display.html?Name=Algorithm-Dependency>
(or L<bug-Algorithm-Dependency@rt.cpan.org|mailto:bug-Algorithm-Dependency@rt.cpan.org>).

=head1 AUTHOR

Adam Kennedy <adamk@cpan.org>

=head1 COPYRIGHT AND LICENSE

This software is copyright (c) 2003 by Adam Kennedy.

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.

=cut