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

Authors

       •   Stevan Little <stevan@cpan.org>

       •   Dave Rolsky <autarch@urth.org>

       •   Jesse Luehrs <doy@cpan.org>

       •   Shawn M Moore <sartak@cpan.org>

       •   יובל קוג'מן (Yuval Kogman) <nothingmuch@woobling.org>

       •   Karen Etheridge <ether@cpan.org>

       •   Florian Ragwitz <rafl@debian.org>

       •   Hans Dieter Pearcey <hdp@cpan.org>

       •   Chris Prather <chris@prather.org>

       •   Matt S Trout <mstrout@cpan.org>

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.

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.

perl v5.40.0                                       2024-10-20              Moose::Cookboo..._ClassMetaclass(3pm)

Description

WARNING:Subclassingmetaclasses(asopposedtoprovidingmetaclasstraits)isstronglydiscouraged.Thisrecipeisprovidedsolelyforreferencewhenencounteringoldercodethatdoesthis.

       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.

Name

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

Synopsis

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

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

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().

   UsingthisMetaclassinPractice
       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');