NAME
Meta::Builder - Tools for creating Meta objects to track custom
metrics.
DESCRIPTION
Meta programming is becoming more and more popular. The popularity of
Meta programming comes from the fact that many problems are made
significantly easier. There are a few specialized Meta tools out there,
for instance Class:MOP which is used by Moose to track class metadata.
Meta::Builder is designed to be a generic tool for writing Meta
objects. Unlike specialized tools, Meta::Builder makes no assumptions
about what metrics you will care about. Meta::Builder also makes it
simple for others to extend your meta-object based tools by providing
hooks for other packages to add metrics to your meta object.
If a specialized Meta object tool is available to meet your needs
please use it. However if you need a simple Meta object to track a
couple metrics, use Meta::Builder.
Meta::Builder is also low-sugar and low-dep. In most cases you will not
want a class that needs a meta object to use your meta-object class
directly. Rather you will usually want to create a sugar class that
exports enhanced API functions that manipulate the meta object.
SYNOPSIS
My/Meta.pm:
package My::Meta;
use strict;
use warnings;
use Meta::Builder;
# Name the accessor that will be defined in the class that uses the meta object
# It is used to retrieve the classes meta object.
accessor "mymeta";
# Add a metric with two actions
metric mymetric => sub { [] },
pop => sub {
my $self = shift;
my ( $data ) = @_;
pop @$data;
},
push => sub {
my $self = shift;
my ( $data, $metric, $action, @args ) = @_;
push @$data => @args;
};
# Add an additional action to the metric
action mymetric => ( get_ref => sub { shift });
# Add some predefined metric types + actions
hash_metric 'my_hashmetric';
lists_metric 'my_listsmetric';
My.pm:
package My;
use strict;
use warnings;
use My::Meta;
My::Meta->new( __PACKAGE__ );
# My::Meta defines mymeta() as the accessor we use to get our meta object.
# this is the ONLY way to get the meta object for this class.
mymeta()->mymetric_push( "some data" );
mymeta()->my_hashmetric_add( key => 'value' );
mymeta()->my_listsmetric_push( list => qw/valueA valueB/ );
# It works fine as an object/class method as well.
__PACKAGE__->mymeta->do_thing(...);
...;
USING
When you use Meta::Builder your class is automatically turned into a
subclass of Meta::Builder::Base. In addition several "sugar" functions
are exported into your namespace. To avoid the "sugar" functions you
can simply subclass Meta::Builder::Base directly.
EXPORTS
metric( $name, \&generator, %actions )
Wrapper around caller-add_metric()>. See Meta::Builder::Base.
action( $metric, $name, $code )
Wrapper around caller-add_action()>. See Meta::Builder::Base.
hash_metric( $name, %additional_actions )
Wrapper around caller-add_hash_metric()>. See Meta::Builder::Base.
lists_metric( $name, %additional_actions )
Wrapper around caller-add_lists_metric()>. See Meta::Builder::Base.
before( $metric, $action, $code )
Wrapper around caller-hook_before()>. See Meta::Builder::Base.
after( $metric, $action, $code )
Wrapper around caller-hook_after()>. See Meta::Builder::Base.
accessor( $name )
Wrapper around caller-set_accessor()>. See Meta::Builder::Base.
make_immutable()
Overrides all functions/methods that alter the meta objects
meta-data. This in effect prevents anything from adding new metrics,
actions, or hooks without directly editing the metadata.
AUTHORS
Chad Granum
[email protected]
COPYRIGHT
Copyright (C) 2010 Chad Granum
Meta-Builder is free software and is licensed under the same terms as
Perl itself.
Meta-Builder is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the license
for more details.
