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package Moose::Cookbook::Meta::Table_MetaclassTrait;
# ABSTRACT: Adding a "table" attribute as a metaclass trait
=pod
=head1 NAME
Moose::Cookbook::Meta::Table_MetaclassTrait - Adding a "table" attribute as a metaclass trait
=head1 VERSION
version 2.0603
=head1 SYNOPSIS
# in lib/MyApp/Meta/Class/Trait/HasTable.pm
package MyApp::Meta::Class::Trait::HasTable;
use Moose::Role;
Moose::Util::meta_class_alias('HasTable');
has table => (
is => 'rw',
isa => 'Str',
);
# in lib/MyApp/User.pm
package MyApp::User;
use Moose -traits => 'HasTable';
__PACKAGE__->meta->table('User');
=head1 DESCRIPTION
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.
=begin testing-SETUP
BEGIN {
package MyApp::Meta::Class::Trait::HasTable;
use Moose::Role;
Moose::Util::meta_class_alias('HasTable');
has table => (
is => 'rw',
isa => 'Str',
);
}
=end testing-SETUP
=head1 THE METACLASS TRAIT
This really is as simple as the recipe L</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
L<Moose::Cookbook::Extending::Debugging_BaseClassRole>, which shows how to
make a module like C<Moose.pm> itself, with sugar like C<has_table()>.
=head2 Using this Metaclass Trait in Practice
Accessing this new C<table> attribute is quite simple. Given a class
named C<MyApp::User>, we could simply write the following:
my $table = MyApp::User->meta->table;
As long as C<MyApp::User> has arranged to apply the
C<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 C<table> method:
$table = MyApp::User->meta->table
if MyApp::User->meta->can('table');
In theory, this is not entirely correct, since the metaclass might be getting
its C<table> method from a I<different> trait. In practice, you are unlikely
to encounter this sort of problem.
=head1 RECIPE CAVEAT
This recipe doesn't work when you paste it all into a single file. This is
because the C<< use Moose -traits => 'HasTable'; >> line ends up being
executed before the C<table> attribute is defined.
When the two packages are separate files, this just works.
=head1 SEE ALSO
L<Moose::Cookbook::Meta::Labeled_AttributeTrait> - Labels implemented via
attribute traits
=for testing can_ok( MyApp::User->meta, 'table' );
is( MyApp::User->meta->table, 'User', 'My::User table is User' );
=head1 AUTHOR
Moose is maintained by the Moose Cabal, along with the help of many contributors. See L<Moose/CABAL> and L<Moose/CONTRIBUTORS> for details.
=head1 COPYRIGHT AND LICENSE
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.
=cut
__END__
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