Moose::Cookbook::Meta::WhyMeta(3) User Contributed Perl Documentation Moose::Cookbook::Meta::WhyMeta(3)
Moose::Cookbook::Meta::WhyMeta - Welcome to the meta world (Why Go Meta?)
You might want to read Moose::Manual::MOP if you haven't done so yet.
If you've ever thought "Moose is great, but I wish it did X differently", then you've gone meta. The meta recipes demonstrate how to change
and extend the way Moose works by extending and overriding how the meta classes (Moose::Meta::Class, Moose::Meta::Attribute, etc) work.
The metaclass API is a set of classes that describe classes, roles, attributes, etc. The metaclass API lets you ask questions about a
class, like "what attributes does it have?", or "what roles does the class do?"
The metaclass system also lets you make changes to a class, for example by adding new methods or attributes.
The interface presented by Moose.pm ("has", "with", "extends") is just a thin layer of syntactic sugar over the underlying metaclass
By extending and changing how this metaclass system works, you can create your own Moose variant.
Let's say that you want to add additional properties to attributes. Specifically, we want to add a "label" property to each attribute, so
we can write "My::Class->meta()->get_attribute('size')->label()". The first recipe shows how to do this using an attribute trait.
You might also want to add additional properties to your metaclass. For example, if you were writing an ORM based on Moose, you could
associate a table name with each class via the class's metaclass object, letting you write "My::Class->meta()->table_name()".
Many of the MooseX modules on CPAN implement metaclass extensions. A couple good examples include MooseX::Aliases and
MooseX::UndefTolerant. For a more complex example see Fey::ORM or Bread::Board::Declare.
Moose is maintained by the Moose Cabal, along with the help of many contributors. See "CABAL" in Moose and "CONTRIBUTORS" in Moose for
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::Meta::WhyMeta(3)