Moose::Cookbook::Meta::Table_ClassMetaclass - Adding a "table" attribute to the metaclass
package MyApp::Meta::Class; use Moose; extends 'Moose::Meta::Class'; has table => ( is => 'rw', isa => 'Str', );
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.
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
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');
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.
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
This software is copyright (c) 2012 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.