---
name: "Meta::Builder"
section: "3pm"
platform: "linux"
package: "libmeta-builder-perl"
version: "0.004-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/Meta::Builder"
---

# Meta::Builder(3pm)

Tools for creating Meta objects to track custom metrics.

## 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.