Here are a few examples where class attributes might come in handy:
-=over
+=over 4
=item *
scope, or you can limit direct data access exclusively to the methods
implementing those attributes.
+=head1 Class Data in a Can
+
+One of the easiest ways to solve a hard problem is to let someone else
+do it for you! In this case, Class::Data::Inheritable (available on a
+CPAN near you) offers a canned solution to the class data problem
+using closures. So before you wade into this document, consider
+having a look at that module.
+
+
=head1 Class Data as Package Variables
Because a class in Perl is really just a package, using package variables
we have much better approaches, like nested hashes or hashes of arrays.
But there's nothing wrong with using symbolic references to manipulate
something that is meaningful only from the perspective of the package
-symbol symbol table, like method names or package variables. In other
+symbol table, like method names or package variables. In other
words, when you want to refer to the symbol table, use symbol references.
Clustering all the class attributes in one place has several advantages.
particular object. The class's eponymous hash can also be used to
implement I<translucent attributes>. A translucent attribute is one
that has a class-wide default. Each object can set its own value for the
-attribute, in which case C<$object-E<gt>attribute()> returns that value.
-But if no value has been set, then C<$object-E<gt>attribute()> returns
+attribute, in which case C<< $object->attribute() >> returns that value.
+But if no value has been set, then C<< $object->attribute() >> returns
the class-wide default.
We'll apply something of a copy-on-write approach to these translucent
module's methods wind up getting compiled.
The usual mealy-mouthed package-mungeing doubtless applies to setting
-up names of object attributes. For example, C<$self-E<gt>{ObData1}>
-should probably be C<$self-E<gt>{ __PACKAGE__ . "_ObData1" }>, but that
+up names of object attributes. For example, C<< $self->{ObData1} >>
+should probably be C<< $self->{ __PACKAGE__ . "_ObData1" } >>, but that
would just confuse the examples.
=head1 SEE ALSO
L<perltoot>, L<perlobj>, L<perlmod>, and L<perlbot>.
-The Tie::SecureHash module from CPAN is worth checking out.
+The Tie::SecureHash and Class::Data::Inheritable modules from CPAN are
+worth checking out.
=head1 AUTHOR AND COPYRIGHT
Copyright (c) 1999 Tom Christiansen.
All rights reserved.
-When included as part of the Standard Version of Perl, or as part of
-its complete documentation whether printed or otherwise, this work
-may be distributed only under the terms of Perl's Artistic License.
-Any distribution of this file or derivatives thereof I<outside>
-of that package require that special arrangements be made with
-copyright holder.
+This documentation is free; you can redistribute it and/or modify it
+under the same terms as Perl itself.
Irrespective of its distribution, all code examples in this file
are hereby placed into the public domain. You are permitted and
=head1 ACKNOWLEDGEMENTS
-Russ Albery, Jon Orwant, Randy Ray, Larry Rosler, Nat Torkington,
+Russ Allbery, Jon Orwant, Randy Ray, Larry Rosler, Nat Torkington,
and Stephen Warren all contributed suggestions and corrections to this
piece. Thanks especially to Damian Conway for his ideas and feedback,
and without whose indirect prodding I might never have taken the time
=head1 HISTORY
-Last edit: Fri May 21 15:47:56 MDT 1999
+Last edit: Sun Feb 4 20:50:28 EST 2001
projects / p5sagit/p5-mst-13.2.git / blobdiff