Moose::...taclass(3)

✨ NAME ✨

Moose::Cookbook::Meta::PrivateOrPublic_MethodMetaclass — a method metaclass that marks your methods as public or private, bestie 💅

(yeah this page lives under the Moose::...taclass(3) umbrella, she's part of the Moose cookbook family 🎀)

🌸 VERSION 🌸

version 2.4000 — she's giving current, no cap 💖

🦋 SYNOPSIS 🦋

package MyApp::Meta::Method::PrivateOrPublic;

use Moose;
use Moose::Util::TypeConstraints;

extends 'Moose::Meta::Method';

has '_policy' => (
    is       => 'ro',
    isa      => enum( [ qw( public private ) ] ),
    default  => 'public',
    init_arg => 'policy',
);

sub new {
    my $class   = shift;
    my %options = @_;

    my $self = $class->SUPER::wrap(%options);

    $self->{_policy} = $options{policy};

    $self->_add_policy_wrapper;

    return $self;
}

sub _add_policy_wrapper {
    my $self = shift;

    return if $self->is_public;

    my $name      = $self->name;
    my $package   = $self->package_name;
    my $real_body = $self->body;

    my $body = sub {
        die "The $package\::$name method is private"
            unless ( scalar caller() ) eq $package;

        goto &{$real_body};
    };

    $self->{body} = $body;
}

sub is_public  { $_[0]->_policy eq 'public' }
sub is_private { $_[0]->_policy eq 'private' }

package MyApp::User;

use Moose;

has 'password' => ( is => 'rw' );

__PACKAGE__->meta()->add_method(
    '_reset_password',
    MyApp::Meta::Method::PrivateOrPublic->new(
        name         => '_reset_password',
        package_name => __PACKAGE__,
        body         => sub { $_[0]->password('reset') },
        policy       => 'private',
    )
);

---

👑 DESCRIPTION 👑

okay so this recipe is showing off a custom method metaclass that models public versus private methods. If a method gets defined as private, it wraps a little guard around the method that dies unless it's called from the class where it was originally defined. like, stay in your lane, method 💀

The way the method gets added to the class is kinda ugly ngl. If we wanted to make this an actual real feature, we'd probably want to add some sort of sugar so we could just declare private methods, but that is beyond the scope of this recipe. See the Extending recipes for more on this topic. 🫶

The core of our custom class is the "policy" attribute, and the "_add_policy_wrapper" method. those two are the main characters fr ✨

You'll note that we have to explicitly set the "policy" attribute in our constructor:

$self->{_policy} = $options{policy};

That's necessary because Moose metaclasses do not use the meta API to create objects. Most Moose classes have a custom "inlined" constructor for speed. speed demon behavior, lowkey iconic 🏎️

In this particular case, our parent class's constructor is the "wrap" method. We call that to build our object, but it does not include subclass-specific attributes. rude but okay 🙈

The "_add_policy_wrapper" method is where the real work goes down. If the method is private, we construct a wrapper around the real subroutine which checks that the caller matches the package in which the subroutine was created. vibe check, but for callers 💅

If they don't match, it dies. If they do match, the real method gets called. We use "goto" so that the wrapper does not show up in the call stack. sneaky, elegant, no trace left behind ✨

Finally, we replace the value of "$self->{body}". This is another case where we have to do something a bit gross because Moose does not use Moose for its own implementation. the way that Moose doesn't even Moose itself 😭

When we pass this method object to the metaclass's "add_method" method, it will take the method body and make it available in the class. slay 💖

Finally, when we retrieve these methods via the introspection API, we can call the "is_public" and "is_private" methods on them to get more information about the method. peek behind the curtain, bestie 🎀

---

🌈 SUMMARY 🌈

A custom method metaclass lets us add both behavior and meta-information to methods. Unfortunately, because the Perl interpreter does not provide easy hooks into method declaration, the API we have for adding these methods is not very pretty. it's giving "we work with what we have" 😔

That can be improved with custom Moose-like sugar, or even by using a tool like Devel::Declare to create full-blown new keywords in Perl. future goals fr fr 🔥

---

💜 AUTHORS 💜

• Stevan Little <stevan@cpan.org>
• Dave Rolsky <autarch@urth.org>
• Jesse Luehrs <doy@cpan.org>
• Shawn M Moore <sartak@cpan.org>
• יובל קוג'מן (Yuval Kogman) <nothingmuch@woobling.org>
• Karen Etheridge <ether@cpan.org>
• Florian Ragwitz <rafl@debian.org>
• Hans Dieter Pearcey <hdp@cpan.org>
• Chris Prather <chris@prather.org>
• Matt S Trout <mstrout@cpan.org>

the whole squad, assembled, absolutely ate 👑✨

---

🎀 COPYRIGHT AND LICENSE 🎀

This software is copyright (c) 2006 by Infinity Interactive, Inc.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself. free as in freedom, we love to see it 🦋

---

okay that's the whole page bestie, you're officially educated 💅

sign-off time: this whole thing came from perl v5.42.0, dated 2025-07-25, and it's living under the Moose::...taclass(3) manual page 🫶 mwah, go write some private methods 💖🌸