NAME<\/a> Moose::Cookbook::Meta::Table_MetaclassTrait \u2212 Adding a “table” attribute as a metaclass trait<\/p>\n version 2.2014<\/p>\n # in lib\/MyApp\/Meta\/Class\/Trait\/HasTable.pm In this recipe, we\u2019ll create a class metaclass trait which has a “table” attribute. This trait is for classes associated with a DBMS<\/small> table, as one might do for an ORM.<\/small><\/p>\n In this example, the table name is just a string, but in a real ORM<\/small> the table might be an object describing the table.<\/p>\n This really is as simple as the recipe ” SYNOPSIS”<\/small> 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 “has_table()”.<\/p>\n Using this Metaclass Trait in Practice<\/b> my $table = MyApp::User\u2212>meta\u2212>table;<\/p>\n 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:<\/p>\n $table = MyApp::User\u2212>meta\u2212>table In theory, this is not entirely correct, since the metaclass might be getting its “table” method from a different<\/i> trait. In practice, you are unlikely to encounter this sort of problem.<\/p>\n This recipe doesn\u2019t work when you paste it all into a single file. This is because the “use Moose \u2212traits => ‘HasTable’;” line ends up being executed before the “table” attribute is defined.<\/p>\n When the two packages are separate files, this just works.<\/p>\n Moose::Cookbook::Meta::Labeled_AttributeTrait \u2212 Labels implemented via attribute traits =pod<\/p>\n \u2022<\/p>\n<\/td>\n Stevan Little \u2022<\/p>\n<\/td>\n Dave Rolsky \u2022<\/p>\n<\/td>\n Jesse Luehrs \u2022<\/p>\n<\/td>\n Shawn M Moore \u2022<\/p>\n<\/td>\n \u00d7\u00d7\u00d7\u00d7 \u00d7\u00a7\u00d7\u00d7\u2019\u00d7\u00d7 (Yuval Kogman) \u2022<\/p>\n<\/td>\n Karen Etheridge \u2022<\/p>\n<\/td>\n Florian Ragwitz \u2022<\/p>\n<\/td>\n Hans Dieter Pearcey \u2022<\/p>\n<\/td>\n
VERSION<\/a>
SYNOPSIS<\/a>
DESCRIPTION<\/a>
THE METACLASS TRAIT<\/a>
RECIPE CAVEAT<\/a>
SEE ALSO<\/a>
AUTHORS<\/a>
COPYRIGHT AND LICENSE<\/a> <\/p>\n
\nNAME <\/a> <\/h2>\n
VERSION <\/a> <\/h2>\n
SYNOPSIS <\/a> <\/h2>\n
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 \u2212traits => ‘HasTable’;
__PACKAGE__\u2212>meta\u2212>table(‘User’);<\/p>\nDESCRIPTION <\/a> <\/h2>\n
THE METACLASS TRAIT <\/a> <\/h2>\n
Accessing this new “table” attribute is quite simple. Given a class named “MyApp::User”, we could simply write the following:<\/p>\n
if MyApp::User\u2212>meta\u2212>can(‘table’);<\/p>\nRECIPE CAVEAT <\/a> <\/h2>\n
SEE ALSO <\/a> <\/h2>\n
AUTHORS <\/a> <\/h2>\n
\n
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