has table => (
is => 'rw',
isa => 'Str',
DESCRIPTIONWARNING: 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 METACLASSThis 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 PracticeAccessing 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');
CONCLUSIONCreating 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.
- Stevan Little <[email protected]>
- Dave Rolsky <[email protected]>
- Jesse Luehrs <[email protected]>
- Shawn M Moore <[email protected]>
- יובל קוג'מן (Yuval Kogman) <[email protected]>
- Karen Etheridge <[email protected]>
- Florian Ragwitz <[email protected]>
- Hans Dieter Pearcey <[email protected]>
- Chris Prather <[email protected]>
- Matt S Trout <[email protected]>
COPYRIGHT AND LICENSEThis 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.