phpman > perldoc > Moose::Cookbook::Legacy::Table_ClassMetaclass

NAME
    Moose::Cookbook::Legacy::Table_ClassMetaclass - Adding a "table" attribute to the metaclass

VERSION
    version 2.2200

SYNOPSIS
      package MyApp::Meta::Class;
      use Moose;
      extends 'Moose::Meta::Class';

      has table => (
          is  => 'rw',
          isa => 'Str',
      );

DESCRIPTION
    WARNING: Subclassing metaclasses (as opposed to providing metaclass traits) is strongly
    discouraged. This recipe is provided solely for reference when encountering older code that does
    this.

    In this recipe, we'll create a new metaclass which has a "table" attribute. This metaclass is
    for classes associated with a DBMS table, as one might do for an ORM.

    In this example, the table name is just a string, but in a real ORM the table might be an object
    describing the table.

THE METACLASS
    This really is as simple as the recipe "SYNOPSIS" shows. The trick is getting your classes to
    use this metaclass, and providing some sort of sugar for declaring the table. This is covered in
    Moose::Cookbook::Extending::Recipe2, which shows how to make a module like "Moose.pm" itself,
    with sugar like "has_table()".

  Using this Metaclass in Practice
    Accessing this new "table" attribute is quite simple. Given a class named "MyApp::User", we
    could simply write the following:

      my $table = MyApp::User->meta->table;

    As long as "MyApp::User" has arranged to use "MyApp::Meta::Class" as its metaclass, this method
    call just works. If we want to be more careful, we can check the metaclass's class:

      $table = MyApp::User->meta->table
          if MyApp::User->meta->isa('MyApp::Meta::Class');

CONCLUSION
    Creating custom metaclass is trivial. Using it is a little harder, and is covered in other
    recipes. We will also talk about applying traits to a class metaclass, which is a more flexible
    and cooperative implementation.

SEE ALSO
    Moose::Cookbook::Meta::Recipe5 - The "table" attribute implemented as a metaclass trait

    Moose::Cookbook::Extending::Recipe2 - Acting like Moose.pm and providing sugar Moose-style

AUTHORS
    *   Stevan Little <stevan AT cpan.org>

    *   Dave Rolsky <autarch AT urth.org>

    *   Jesse Luehrs <doy AT cpan.org>

    *   Shawn M Moore <sartak AT cpan.org>

    *   יובל קוג'מן (Yuval Kogman) <nothingmuch AT woobling.org>

    *   Karen Etheridge <ether AT cpan.org>

    *   Florian Ragwitz <rafl AT debian.org>

    *   Hans Dieter Pearcey <hdp AT cpan.org>

    *   Chris Prather <chris AT prather.org>

    *   Matt S Trout <mstrout AT cpan.org>

COPYRIGHT AND LICENSE
    This software is copyright (c) 2006 by Infinity Interactive, Inc.

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