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.

METHODS

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:

  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 Employee;
  use base 'Person';

  sub DEFAULTS {
    salary => 10_000,
  }


  package LocatedEmployee;
  use base 'Employee';

  # Note: no default for address, but different salary

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


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

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

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 2004-2007 by Marcel Grünauer

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