Moose::Cookbook::Meta::Recipe4(3pm)
NAME
Moose::Cookbook::Meta::Recipe4 - Adding a "table" attribute to the
metaclass
SYNOPSIS
package MyApp::Meta::Class;
use Moose;
extends 'Moose::Meta::Class';
has table => (
is => 'rw',
isa => 'Str',
);
DESCRIPTION
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->tableif 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
AUTHOR
Dave Rolsky <autarch@urth.org>
COPYRIGHT AND LICENSE
Copyright 2006-2010 by Infinity Interactive, Inc.
<http://www.iinteractive.com>
- This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.