/ 
Data-Inherited-1.00
River stage two • 10 direct dependents • 35 total dependents
/ Data::Inherited

NAME

Data::Inherited - hierarchy-wide accumulation of list and hash results

VERSION

This document describes version 1.00 of Data::Inherited.

SYNOPSIS

package Foo;
use base 'Data::Inherited';
use constant PROPERTIES => (qw/name address/);

package Bar;
use base 'Foo';
use constant PROPERTIES => (qw/age/);

package main;
my $bar = Bar->new;
print "$_\n" for $bar->every_list('PROPERTIES');

prints

name
address
age

DESCRIPTION

This is a mixin class. By inheriting from it you get two methods that are able to accumulate hierarchy-wide list and hash results.

every_list(String $method_name, Bool ?$override_cache = 0)

Takes as arguments a method name (mandatory) and a boolean indicating whether to override the cache (optional, off by default)

Causes every method in the object's hierarchy with the given name to be invoked. The resulting list is the combined set of results from all the methods, pushed together in top-to-bottom order (hierarchy-wise).

every_list() returns a list in list context and an array reference in scalar context.

The result is cached (per calling package) and the next time the method is called from the same package with the same method argument, the cached result is returned. This is to speed up method calls, because internally this module uses NEXT, which is quite slow. It is expected that every_list() is used for methods returning static lists (object defaults, static class definitions and such). If you want to override the caching mechanism, you can provide the optional second argument. The result is cached in any case.

See the synopsis for an example.

every_hash(String $method_name, Bool ?$override_cache = 0)

Takes as arguments a method name (mandatory) and a boolean indicating whether to override the cache (optional, off by default)

Causes every method in the object's hierarchy with the given name to be invoked. The resulting hash is the combined set of results from all the methods, overlaid in top-to-bottom order (hierarchy-wise).

every_hash() returns a hash in list context and a hash reference in scalar context.

The cache and the optional cache override argument work like with every_list().

Example (see Class::MethodMaker::Util for a full implementation of instance defaults and much more):

package Person;
use base 'Data::Inherited';

sub new {
  my $class = shift;
  my $self = bless {}, $class;
  my %args = @_;
  %args = ($self->every_hash('DEFAULTS'), %args);
  $self->$_($args{$_}) for keys %args;
  $self;
};

sub DEFAULTS {
  first_name => 'John',
  last_name  => 'Smith',
};


package Sarariman;
use base 'Person';

sub DEFAULTS {
  salary => 10_000,
}


package LocatedSarariman;
use base 'Sarariman';

# Note: no default for address, but different salary

sub DEFAULTS { 
  salary     => 20_000,
  first_name => 'Johan',
}


package main;
my $p = LocatedSarariman->new;

# salary: 20000
# first_name: Johan
# last_name: Smith

DIAGNOSTICS

There are no diagnostics for this module.

INCOMPATIBILITIES

This module relies on NEXT. Until an updated version of NEXT is released, Data::Inherited includes a modified version of NEXT that avoids a subtle bug when used within the stringification method of an overloaded object (patch submitted to the author). It's included within the this file so as to not clutter perl's lib directory, as it's only a temporary measure. Moreover, NEXT is a core perl module, but Data::Inheritance installs in site_perl, leading to potentially more confusion.

We make perl believe that NEXT is loaded so it won't overwrite our changes with the original NEXT if somewhere it says use NEXT.

BUGS AND LIMITATIONS

No bugs have been reported.

Please report any bugs or feature requests to bug-data-inherited@rt.cpan.org, or through the web interface at http://rt.cpan.org.

INSTALLATION

See perlmodinstall for information and options on installing Perl modules.

AVAILABILITY

The latest version of this module is available from the Comprehensive Perl Archive Network (CPAN). Visit <http://www.perl.com/CPAN/> to find a CPAN site near you. Or see <http://www.perl.com/CPAN/authors/id/M/MA/MARCEL/>.

AUTHOR

Marcel Grünauer, <marcel@cpan.org>

COPYRIGHT AND LICENSE

Copyright 2004-2005 by Marcel Grünauer

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

DISCLAIMER OF WARRANTY

BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR, OR CORRECTION.

IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.