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moose::cookbook::meta::recipe5(3) [osx man page]

Moose::Cookbook::Meta::Recipe5(3)			User Contributed Perl Documentation			 Moose::Cookbook::Meta::Recipe5(3)

Moose::Cookbook::Meta::Recipe5 - The "table" attribute as a metaclass trait VERSION
version 2.0205 SYNOPSIS
package MyApp::Meta::Class::Trait::HasTable; use Moose::Role; has table => ( is => 'rw', isa => 'Str', ); package Moose::Meta::Class::Custom::Trait::HasTable; sub register_implementation { 'MyApp::Meta::Class::Trait::HasTable' } package MyApp::User; use Moose -traits => 'HasTable'; __PACKAGE__->meta->table('User'); DESCRIPTION
This recipe takes the metaclass table attribute from Moose::Cookbook::Meta::Recipe4 and implements it as a metaclass trait. Traits are just roles, as we saw in Moose::Cookbook::Meta::Recipe3. The advantage of using traits is that it's easy to combine multiple traits, whereas combining multiple metaclass subclasses requires creating yet another subclass. With traits, Moose takes care of applying them to your metaclass. Using this Metaclass Trait in Practice Once this trait has been applied to a metaclass, it looks exactly like the example we saw in Moose::Cookbook::Meta::Recipe4: my $table = MyApp::User->meta->table; # the safe version $table = MyApp::User->meta->table if MyApp::User->meta->meta->can('does') and MyApp::User->meta->meta->does('MyApp::Meta::Class'); The safe version is a little complicated. We have to check that the metaclass object's metaclass has a "does" method, in which case we can ask if the the metaclass does a given role. It's simpler to just write: $table = MyApp::User->meta->table if MyApp::User->meta->can('table'); In theory, this is a little less correct, since the metaclass might be getting its "table" method from a different role. In practice, you are unlikely to encounter this sort of problem. SEE ALSO
Moose::Cookbook::Meta::Recipe3 - Labels implemented via attribute traits Moose::Cookbook::Meta::Recipe4 - Adding a "table" attribute to the metaclass AUTHOR
This software is copyright (c) 2011 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. perl v5.12.5 2011-09-06 Moose::Cookbook::Meta::Recipe5(3)

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Moose::Cookbook::Legacy::Table_ClassMetaclass(3)	User Contributed Perl Documentation	  Moose::Cookbook::Legacy::Table_ClassMetaclass(3)

Moose::Cookbook::Meta::Table_ClassMetaclass - Adding a "table" attribute to the metaclass VERSION
version 2.0604 SYNOPSIS
package MyApp::Meta::Class; use Moose; extends 'Moose::Meta::Class'; has table => ( is => 'rw', isa => 'Str', ); DESCRIPTION
WARNING: 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 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 "" 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->table if 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 and providing sugar Moose-style AUTHOR
Moose is maintained by the Moose Cabal, along with the help of many contributors. See "CABAL" in Moose and "CONTRIBUTORS" in Moose for details. 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. perl v5.16.2 2012-09-19 Moose::Cookbook::Legacy::Table_ClassMetaclass(3)
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