Chad Granum > Meta-Builder-0.003 > Meta::Builder



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


Meta programming is becomming 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 mkaes 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 ot 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.



    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';

    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.



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 sublass Meta::Builder::Base directly.


metric( $name, \&generator, %actions )

Wraper around caller-add_metric()>. See Meta::Builder::Base.

action( $metric, $name, $code )

Wraper around caller-add_action()>. See Meta::Builder::Base.

hash_metric( $name, %additional_actions )

Wraper around caller-add_hash_metric()>. See Meta::Builder::Base.

lists_metric( $name, %additional_actions )

Wraper around caller-add_lists_metric()>. See Meta::Builder::Base.

before( $metric, $action, $code )

Wraper around caller-hook_before()>. See Meta::Builder::Base.

after( $metric, $action, $code )

Wraper around caller-hook_after()>. See Meta::Builder::Base.

accessor( $name )

Wraper around caller-set_accessor()>. See Meta::Builder::Base.


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.


Chad Granum


Copyright (C) 2010 Chad Granum

Meta-Builder is free software; Standard perl licence.

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.

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