Rename Meta::Recipe1 to Meta::WhyMeta

[gitmo/Moose.git] / lib / Moose / Cookbook / Meta / WhyMeta.pod

package Moose::Cookbook::Meta::WhyMeta;

# ABSTRACT: Welcome to the meta world (Why Go Meta?)

__END__


=pod

=head1 SUMMARY

You might want to read L<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 (L<Moose::Meta::Class>,
L<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 L<Moose.pm|Moose> (C<has>, C<with>,
C<extends>) is just a thin layer of syntactic sugar over the
underlying metaclass system.

By extending and changing how this metaclass system works, you can
create your own Moose variant.

=head2 Examples

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 C<<
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 C<< My::Class->meta()->table_name() >>.

=head1 SEE ALSO

Many of the MooseX modules on CPAN implement metaclass extensions. A
couple good examples include L<MooseX::Aliases> and
L<MooseX::UndefTolerant>. For a more complex example see
L<Fey::ORM> or L<Bread::Board::Declare>.

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