moose::cookbook::meta::whymeta(3pm) [debian man page]

Moose::Cookbook::Meta::WhyMeta(3pm)			User Contributed Perl Documentation		       Moose::Cookbook::Meta::WhyMeta(3pm)

NAME

       Moose::Cookbook::Meta::WhyMeta - Welcome to the meta world (Why Go Meta?)

VERSION

       version 2.0603

SUMMARY

       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
       system.

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

   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 "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()".

SEE ALSO

       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.

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 v5.14.2							    2012-06-28				       Moose::Cookbook::Meta::WhyMeta(3pm)

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

NAME

       Moose::Cookbook::Meta::Table_ClassMetaclass - Adding a "table" attribute to the metaclass

VERSION

       version 2.0603

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 "Moose.pm"
       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 Moose.pm 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 v5.14.2							    2012-06-28			Moose::Cookbook::Legacy::Table_ClassMetaclass(3pm)