158 lines
3.4 KiB
Plaintext
158 lines
3.4 KiB
Plaintext
# PODNAME: Moose::Cookbook::Meta::Table_MetaclassTrait
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# ABSTRACT: Adding a "table" attribute as a metaclass trait
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__END__
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=pod
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=encoding UTF-8
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=head1 NAME
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Moose::Cookbook::Meta::Table_MetaclassTrait - Adding a "table" attribute as a metaclass trait
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=head1 VERSION
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version 2.2207
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=head1 SYNOPSIS
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# in lib/MyApp/Meta/Class/Trait/HasTable.pm
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package MyApp::Meta::Class::Trait::HasTable;
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use Moose::Role;
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Moose::Util::meta_class_alias('HasTable');
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has table => (
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is => 'rw',
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isa => 'Str',
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);
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# in lib/MyApp/User.pm
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package MyApp::User;
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use Moose -traits => 'HasTable';
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__PACKAGE__->meta->table('User');
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=head1 DESCRIPTION
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In this recipe, we'll create a class metaclass trait which has a "table"
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attribute. This trait is for classes associated with a DBMS table, as one
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might do for an ORM.
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In this example, the table name is just a string, but in a real ORM
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the table might be an object describing the table.
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=begin testing-SETUP
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BEGIN {
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package MyApp::Meta::Class::Trait::HasTable;
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use Moose::Role;
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Moose::Util::meta_class_alias('HasTable');
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has table => (
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is => 'rw',
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isa => 'Str',
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);
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}
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=end testing-SETUP
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=head1 THE METACLASS TRAIT
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This really is as simple as the recipe L</SYNOPSIS> shows. The trick is
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getting your classes to use this metaclass, and providing some sort of sugar
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for declaring the table. This is covered in
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L<Moose::Cookbook::Extending::Debugging_BaseClassRole>, which shows how to
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make a module like C<Moose.pm> itself, with sugar like C<has_table()>.
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=head2 Using this Metaclass Trait in Practice
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Accessing this new C<table> attribute is quite simple. Given a class
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named C<MyApp::User>, we could simply write the following:
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my $table = MyApp::User->meta->table;
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As long as C<MyApp::User> has arranged to apply the
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C<MyApp::Meta::Class::Trait::HasTable> to its metaclass, this method call just
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works. If we want to be more careful, we can check that the class metaclass
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object has a C<table> method:
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$table = MyApp::User->meta->table
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if MyApp::User->meta->can('table');
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In theory, this is not entirely correct, since the metaclass might be getting
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its C<table> method from a I<different> trait. In practice, you are unlikely
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to encounter this sort of problem.
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=head1 RECIPE CAVEAT
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This recipe doesn't work when you paste it all into a single file. This is
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because the C<< use Moose -traits => 'HasTable'; >> line ends up being
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executed before the C<table> attribute is defined.
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When the two packages are separate files, this just works.
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=head1 SEE ALSO
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L<Moose::Cookbook::Meta::Labeled_AttributeTrait> - Labels implemented via
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attribute traits
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=pod
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=for testing can_ok( MyApp::User->meta, 'table' );
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is( MyApp::User->meta->table, 'User', 'My::User table is User' );
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=head1 AUTHORS
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=over 4
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=item *
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Stevan Little <stevan@cpan.org>
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=item *
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Dave Rolsky <autarch@urth.org>
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=item *
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Jesse Luehrs <doy@cpan.org>
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=item *
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Shawn M Moore <sartak@cpan.org>
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=item *
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יובל קוג'מן (Yuval Kogman) <nothingmuch@woobling.org>
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=item *
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Karen Etheridge <ether@cpan.org>
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=item *
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Florian Ragwitz <rafl@debian.org>
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=item *
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Hans Dieter Pearcey <hdp@cpan.org>
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=item *
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Chris Prather <chris@prather.org>
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=item *
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Matt S Trout <mstrout@cpan.org>
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=back
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=head1 COPYRIGHT AND LICENSE
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This software is copyright (c) 2006 by Infinity Interactive, Inc.
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This is free software; you can redistribute it and/or modify it under
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the same terms as the Perl 5 programming language system itself.
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=cut
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