package Class::Adapter;
=pod
=head1 NAME
Class::Adapter - Perl implementation of the "Adapter" Design Pattern
=head1 DESCRIPTION
The C<Class::Adapter> class is intended as an abstract base class for
creating any sort of class or object that follows the I<Adapter> pattern.
=head2 What is an Adapter?
The term I<Adapter> refers to a I<"Design Pattern"> of the same name,
from the famous I<"Gang of Four"> book I<"Design Patterns">. Although
their original implementation was designed for Java and similar
single-inheritance strictly-typed langauge, the situation for which it
applies is still valid.
An I<Adapter> in this Perl sense of the term is when a class is created
to achieve by composition (objects containing other object) something that
can't be achieved by inheritance (sub-classing).
This is similar to the I<Decorator> pattern, but is intended to be
applied on a class-by-class basis, as opposed to being able to be applied
one object at a time, as is the case with the I<Decorator> pattern.
The C<Class::Adapter> object holds a parent object that it "wraps",
and when a method is called on the C<Class::Adapter>, it manually
calls the same (or different) method with the same (or different)
parameters on the parent object contained within it.
Instead of these custom methods being hooked in on an object-by-object
basis, they are defined at the class level.
Basically, a C<Class::Adapter> is one of your fall-back positions
when Perl's inheritance model fails you, or is no longer good enough,
and you need to do something twisty in order to make several APIs play
nicely with each other.
=head2 What can I do with the actual Class::Adapter class
Well... nothing really. It exist to provide some extremely low level
fundamental methods, and to provide a common base for inheritance of
Adapter classes.
The base C<Class::Adapter> class doesn't even implement a way to push
method calls through to the underlying object, since the way in which
B<that> happens is the bit that changes from case to case.
To actually DO something, you probably want to go take a look at
L<Class::Adapter::Builder>, which makes the creation of I<Adapter>
classes relatively quick and easy.
=head1 METHODS
The C<Class::Adapter> class itself supplies only the two most common
methods, a default constructor and a private method to access the
underlying object.
=cut
use 5.005;
use strict;
use Carp ();
use Scalar::Util 1.10 ();
use vars qw{$VERSION};
BEGIN {
$VERSION = '1.08';
}
#####################################################################
# Constructor
=pod
=head2 new $object
The default C<new> constructor takes a single object as argument and
creates a new object which holds the passed object.
Returns a new C<Class::Adapter> object, or C<undef> if you do not pass
in an object.
=cut
sub new {
my $class = ref $_[0] ? ref shift : shift;
my $object = Scalar::Util::blessed($_[0]) ? shift : return undef;
return bless { OBJECT => $object }, $class;
}
#####################################################################
# Private Methods
=pod
=head2 _OBJECT_
The C<_OBJECT_> method is provided primarily as a convenience, and a tool
for people implementing sub-classes, and allows the C<Class::Adapter>
interface to provide a guarenteed correct way of getting to the underlying
object, should you need to do so.
=cut
sub _OBJECT_ {
return $_[0]->{OBJECT} if ref $_[0];
Carp::croak('Class::Adapter::_OBJECT_ called as a static method');
}
1;
=pod
=head1 SUPPORT
Bugs should be reported via the CPAN bug tracker at
L<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Class-Adapter>
For other issues, contact the author.
=head1 TO DO
- Write more comprehensive tests
=head1 AUTHOR
Adam Kennedy E<lt>adamk@cpan.orgE<gt>
=head1 SEE ALSO
L<Class::Adapter::Clear>, L<Class::Adapter::Builder>, L<Class::Decorator>
=head1 COPYRIGHT
Copyright 2005 - 2011 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.
=cut