Moose::Cookbook::Meta::Table_MetaclassTrait - Adding a "table"
attribute as a metaclass trait
# in lib/MyApp/Meta/Class/Trait/HasTable.pm
has table => (
is => 'rw',
isa => 'Str',
# in lib/MyApp/User.pm
use Moose -traits => 'HasTable';
In this recipe, we'll create a class metaclass trait which has a
"table" attribute. This trait 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::Debugging_BaseClassRole, 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 apply the
"MyApp::Meta::Class::Trait::HasTable" to its metaclass, this method
call just works. If we want to be more careful, we can check that the class
metaclass object has a "table" method:
$table = MyApp::User->meta->table
In theory, this is not entirely correct, since the metaclass might be getting
its "table" method from a different
trait. In practice, you
are unlikely to encounter this sort of problem.
This recipe doesn't work when you paste it all into a single file. This is
because the "use Moose -traits => 'HasTable';" line ends up being
executed before the "table" attribute is defined.
When the two packages are separate files, this just works.
Moose::Cookbook::Meta::Labeled_AttributeTrait - Labels implemented via attribute
- Stevan Little <firstname.lastname@example.org>
- Dave Rolsky <email@example.com>
- Jesse Luehrs <firstname.lastname@example.org>
- Shawn M Moore <email@example.com>
- יובל קוג'מן
(Yuval Kogman) <firstname.lastname@example.org>
- Karen Etheridge <email@example.com>
- Florian Ragwitz <firstname.lastname@example.org>
- Hans Dieter Pearcey <email@example.com>
- Chris Prather <firstname.lastname@example.org>
- Matt S Trout <email@example.com>
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.