Meta::Builder - Tools for creating Meta objects to track custom metrics.

- NAME
- DESCRIPTION
- SYNOPSIS
- USING
- EXPORTS
- AUTHORS
- COPYRIGHT

# 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 exodist7@gmail.com

# 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.

Meta::Builder - Tools for creating Meta objects to track custom metrics.