Meta::Builder3pm

Usage

    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.
    __PACKAGE__->mymeta->do_thing(...);
    ...;

Overview

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.

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.